Republic of Iraq

Ministry of Higher Education

& Scientific Research

University of Baghdad

College of Science

Integrated effect of sunflower residues and

chevalier on weeds of wheat and growth of

mycorrhiza.

A Thesis Submitted to the Council of the College of Science,

Department of Biology, University of Baghdad as a Partial

Fulfillment of the Requirements for the Degree of Doctor of

Philosophy (Ph.D.)

in Plant Physiology, Botany.

By

Srraaۥ Nsayef Muslim Al-Eqaili

B. Sc. Microbiology/ College of Science/ University of

Mustansiriya 2006

M.Sc. Botany/ College of Science/ University of Mustansiriya

2009.

Supervised By

Ibrahim S. Alsaadawi Dr. Hadi M. Aboud Prof. Dr.

2014 A. H. 1435 A. D.

الرحيـمبســم هللا الرحمـن

يسجد له من في السماوات ومن في األرض ا﴿ لم تر أن الل والقمر والنجوم والجبـال والشجر والدواب وكثير والشمس

فما له وكثير من النـاس حق عليه العذاب ومن يهن الل يفعل ما يشاء ﴾ من مكرم إن الل

صـدق هللا الـعـظيم (81سورة الحج ) أية

This is to certify that the thesis titled: " Integrated effect of

sunflower residues and chevalier on weeds of wheat and growth of

mycorrhiza ".

Submitted by: Srraaۥ Nsayef Muslim Al-Eqaili

Department: Biology

College: Science

has been linguistically corrected and its language, in its present form, is

acceptable.

Name: Professor Shatha K. AL-Saadi

Address: Department of English, College of Education for Women,

University of Baghdad

Signature:

SUPERVISOR CERTIFICATION

We certify that thesis entitled '' Integrated effect of sunflower

residues and chevalier on weeds of wheat and growth of mycorrhiza

'' is prepared by " Srraaۥ Nsayef Muslim Al-Eqaili " under our

supervision at the College of Science, University of Baghdad in partial

fulfillment of requirements for the degree of Doctor of Philosophy in

Biology.

Signature:

Name : Dr. Ibrahim S. Alsaadawi

Title : Professor

Address : College of Science,

Department of Biology, University of

Baghdad.

Date: / / 2014

Signature:

Name : Dr. Hadi M. Aboud

Title : Chief Scientific Researchers

Address: Agricultural Research Center,

Ministry of Science and Technology.

Date: / / 2014

In view of the available recommendation, I forward this thesis for debate

by the examination committee.

Signature:

Dr. Sabah N. Alwachi

Title: Professor

Head Department of Biology

Date: / / 2014

Committee Certification We, the Examining Committee, certify that we have read this thesis in

titled '' Integrated effect of sunflower residues and chevalier on weeds

of wheat and growth of mycorrhiza '' and have examined the student

"Srraa Nsayef Muslim Al-Eqaili" in its contents and that in our opinion; it is

accepted as a thesis for awarding the Degree of Doctor of Philosophy in

Biology.

Dr. Abd oun H. Alwan Dr. Abdullah I. Shaheed

Professor Professor

Member Member

/ / 2014 / / 2014

Dr. Risan K. Shatti Dr. Ayyad W. AL-Shahwany

Professor Assist. Professor

Member Member

/ / 2014 / / 2014

Dr. Muna H. Al Jubori

Professor

Chairman

/ /2014

Dr. Ibrahim S. Alsaadawi Dr. Hadi M. Aboud

Professor Chief Scientific Researchers

(Advisor) (Advisor)

/ /2014 / / 2014

Approved for the College of committee of graduate studies

Assist. Professor Dr. Mohammad A. Atiya

Dean

College of Science, Baghdad University

/ / 2014

Acknowledgment

First of all, I would like to thank the grace of God for completing

this work at this final shape. All respects are for His Holy Prophet

Mohammad (Peace be upon him and his family), for enlightening our

conscience with the essence of faith in Allah.

My deepest thanks and gratitude to my supervisor, Dr. Ibrahim

Alsaadawi and Dr. Hadi M. Aboud for supervision, scientific guidance,

helpful discussion, generosity, providing the possible laboratory

materials and support during all the period of the research.

Many thanks to the Head of the Department of Biology, College of

Science, University of Baghdad, also I am grateful to Dr. Hind Hussain

for her help and moral support. Appreciation is extended to Dean of

College of Science, University of Baghdad.

Deep thanks to Dr. Nabil R. Al-bedairy from University of

Wasit who enable me, with their endless support, and encouragement to

complete this thesis , also to Mrs. Falah Abdul Hassan from Dept. of

Food analysis.

Finally, I would like to express my sincere thanks and gratitude to all my

best friends (Hamed, Ali, Ala, laith, Tamara, Arwa) who enable me,

with their endless support, and encouragement to complete this thesis.

Dedication

I dedicate the fruit of my efforts

To those who taught us letters of gold and

words of jewel of the utmost and sweetest

sentences in the whole knowledge… My supervisors

To the Spring that never stops giving, who

weaves my happiness with strings from her

merciful heart… The pure soul of my lovely mother

To whose love flows in my veins, and my heart always

remembers them… My brothers and sisters

Srraۥa

Abstract

A set of experiments was performed to test the allelopathic

potential of sunflower residues alone or in combination with reduced rate

(50% of recommended dose) of chevalier herbicide on weeds, wheat crop

and growth of mycorrhiza associated with wheat roots. The field

experiment was conducted during 2012-2013 season at the Research

Farm of Biology Department, College of Science, Baghdad University by

using the randomized complete block design (RCBD) with 4 replications

to test the effect of sunflower residues at 3 and 6 t ha-1

alone or in

combination with reduced dose of Chevalier (150 g ha-1

) on weed and

wheat crop. Weedy check and label rate of chevalier were also included

for comparison. Each treatment was replicated four times. Total

phenolics in field soil amended with sunflower residues at 6 t ha-1

was

determined during different periods after sowing. Mycorrhizal sporulation

was determined during different growth stages of wheat and colonization

rate and intensity were determined at flowering stage of wheat.

Result showed that incorporation of sunflower residues at 3 t ha-1

reduced weed density by 88 and 97% of control after 90 and 120 days

after sowing (DAS), respectively. The reduction was increased when

sunflower residues were incorporated at 6 t ha-1

and reached to 89 and

78% of the control after 90 and 120 DAS, respectively. However, the

suppression of weed population and dry weight biomass was further

improved when the plots were treated with 50% of labeled rate of

herbicide and amended with sunflower residues. Integration of reduced

herbicide rate and sunflower residues at 3 t ha-1

and 6 t ha-1

resulted in

more weed suppression than sole application of the respected sunflower

residues.

The results also revealed that weed suppression was directly

translated into yield of wheat. Application of Chevalier herbicide at 50%

rate in plots amended with sunflower residue at rates of 3 t ha-1

resulted in

similar biological and grain yields, number of spikes per plant, number of

grains per spike and harvest index was achieved by the label herbicide

rate treatment.

Chemical analyses indicated that total phenolics started to

increase at 14 and 28 days of decomposition and declined thereafter until

vanished 6 weeks of decomposition. Biological activity test of field soil

revealed that suppression of Malva rotundifolia weed was highly

correlated with total phenolics of soil suggesting that high weed

suppression was mainly due to high activity of phenolics.

With respect to mycorrhizal studies, the number of spores in field

soil amended with sunflower residues was significantly increased at 2, 4

and 6 weeks of residue decomposition compared to the control treatment

(without sunflower residue). At flowering stage, it was found that

chevalier at reduced (50% of the label rate) rate applied to plots amended

with sunflower residue at 3 t ha-1

scored spore number significantly lower

than that of the control treatment, but when the reduced dose was applied

to plots amended with higher residues rate, the number of spores was

significantly increased over the control. Sunflower residues incorporated

in to field soil at rates of 3 t ha-1

increased rate and intensity of

colonization by 49% and 44% of control, respectively. Application of

reduced dose of herbicide on plants grown in plots amended with

sunflower residues significantly increased rate of colonization compared

to the control.

List of Contents Item

No. Item Page No.

Abstract I

List of contents Ш

List of tables VII

List of figures X

Chapter one

Literatures review

Introduction 1

1 Literatures review 4

1.1. Allelopathy of crop on weeds 4

1.1.1 Effect of allelopathic plant extracts 5

1.1.2. Effects of allelopathic crop residues 11

1.1.3. Combined effect of allelopathic extract with

herbicides

19

1.1.4. Combined effect of allelopathic residues with

herbicides

26

1.2 Effect of phenolic compounds on arbuscular

mycorrhiza

29

Chapter two

Material and methods

2 Material and methods 35

2.1 Field preparations 35

2.1.1. Site selection 35

2.1.2. Seeds and herbicides sources 35

2.1.3. Soil Sampling and Analyses 35

2.1.4. Preparation of sunflower residues 37

2.2. Field trial 37

2.3 Weed measurements 38

2.3.1. Weed density (plant m‾2) 38

2.3.2. Weed biomass (g m‾2) 39

2.4. Wheat crop measurements 39

2.4.1. Dry weight of plant through different stages of

crop growth (g/m2)

39

2.4.2. Crop Growth Rate CGR (g/m2/day) 39

2.4.3. Plant height 40

2.4.4. Number of spikes/m2 40

2.4.5. Number of grains per spike 40

2.4.6. 1000-grain weight (g) 40

2.4.7. Total wheat biomass (t ha1ـ) 40

2.4.8. Grain yield (t haـ 1) 40

2.4.9. Biological yield 41

2.4.10. Harvest index (%) 41

2.5. Mycorrhizal studies 41

2.5.1. Spore extraction 41

2.5.2. Isolation and identification of mycorrhiza spores 42

2.5.3. Preparation of Mycorrhiza inoculums 42

2.5.4. Spore counting 42

2.5.5. Mycorrhizal colonization rate (%) 43

2.6. Determination of total phenolics 44

2.7. Bioassay of soil amended with sunflower

residues

45

2.8. statistical analyzsis 45

Chapter three

Results

3 Results 46

3.1. Weed parameter 46

3.1.1. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

total weed density in wheat field

46

3.1.2. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

dry weight biomass of weeds in wheat.

49

3.2. Crop parameters 49

3.2.1 Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

dry weight of wheat during different growth

stages.

49

3.2.2 Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

crop growth rate of wheat crop

52

3.2.3. Grain yield (t ha-1

) 52

3.2.4. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

yield components of wheat

55

3.2.4.1. Effect on number of spikes per m2 55

3.2.4.2. Effect on grains per spike 55

3.2.4.3. Effect on 1000-grain weight (g) 56

3.2.5. Biological yield (t ha-1

) 59

3.2.6. Biomass (t ha-1

) 59

3.2.7. Harvest index % 61

3.2.8. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

plant height of wheat

62

3.3. Determination of Total phenolics in field soil 63

3.4. Weed bioassay 64

3.4.1. Seed germination of malva rotundifolia 64

3.4.2. Total dry weight of Malva rotundifolia 65

3.5. Mycorrhizal studies 66

3.5.1. Isolation and identification of mycorrhiza from

field soil of wheat crop

66

3.5.2. Effect of different periods of decomposition of

sunflower residues in field soil before chevalier

application on sporulation

67

3.5.3. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

sporulation at flowering stage

68

3.5.4. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

colonization rate of Glomus mosseae

68

3.5.5. Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

colonization intensity of Glomus mosseae

71

4 Chapter four-Discussion 72

5 Conclusions and Recommendations 79

6 References 81

7 Appendices 103

8 Abstract in Arabic

List of tables

No. Title Page

1

Some Physical and chemical properties of field

soil before and after sunflower residue

incorporation.

36

2 Weed species grown in the test wheat field. 47

3

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

weeds population grown in wheat .

48

4

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

dry weight biomass of weeds grown in wheat.

50

5

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on grain yield of wheat crop.

54

6

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on number of spikes of wheat.

56

7

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on number of grains per spike of wheat.

57

8

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on weight of 1000 grains of wheat.

58

9

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on biological yield of wheat crop.

60

10

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

biomass of wheat.

60

11

Effect of different rates of chevalier 15

WG herbicide and sunflower residues

cv. Asgrow on number of spores of

Glomus mosseae associated with wheat

roots.

69

12

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on colonization rate of Glomus mosseae

associated with wheat roots.

70

13

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on colonization intensity Glomus mosseae

associated with wheat roots.

71

List of figure

No. Title Page

1

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

dry weight of wheat.

51

2

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow on

crop growth rate of wheat.

53

3

Effect of different rates of chevalier15 WG

herbicide and sunflower residues cv. Asgrow

on Harvest index of wheat.

61

4

Effect of different rates of chevalier 15 WG

herbicide and sunflower residues cv. Asgrow

on plant height of wheat.

62

5

Total phenolics released in field soil amended

with sunflower residues at 6 t ha-1

during

different decomposition periods.

63

6

Seed germination of Malva rotundifolia in field

soil amended with sunflower residues at 6 t ha-1

during different decomposition periods.

64

7

Total dry weight of Malva rotundifolia in field

soil amended with sunflower residues at 6 t ha-1

during different decomposition periods.

65

8 spore of Glomus mosseae 66

9 Sporocarp 66

10

Sporulation of Glomus mosseae in field soil

amended with sunflower residues at 6 t ha-1

during different decomposition periods.

67

Introduction

Introduction

Weeds represent a global agronomic problem that reduces the

productivity of cultivated crops. Weeds compete with cultivated crops for

the available moisture, nutrients and light. Consequently, weeds

significantly reduce either crop yield or quality. Control of weeds is

essential to maintaining the production of economic crops. Currently,

Agriculture worldwide is using about 3 million tons of herbicides per

year, and herbicide-resistant weeds have become more prolific, which has

further expanded the use of herbicides (Shibayama, 2001). The overuse of

agrochemicals has caused environmental pollution, weed tolerance and

human health concerns. To solve these problems, it is necessary to

develop sustainable weed management systems that may reduce herbicide

dependency, inexpensive, easy to use and helpful in maintaining the

ecosystem stability (Khanh et al., 2013).

Allelopathy has been accepted as environment-friendly

phenomenon, which may prove to be a useful means for weed

management and thereby increase crop yields (Putnam et al., 1983). It

involves direct or indirect effects of one plant on another through the

production of secondary chemical compounds that escape into the

environment (Rice, 1984). Chemicals with allelopathic potential are

present in virtually all plant parts or tissue. These allelochemicals offer

great potential as natural pesticides and can be used for weed control

directly or their chemistry could be used to develop new herbicides

(Putnam et al, 1990). However, in most cases, allelopathic extracts or

crop residues provide limited weed suppression, and most often

reductions in weed growth are not comparable to those observed with

labeled herbicides. Therefore, other methods to increase the efficacy of

allelopathic extracts may be critical to enhance weed suppression while at

the same time reducing our reliance on herbicides. Substantial scope to

reduce the herbicide rate has been observed by various investigators when

herbicides are applied together with aqueous sorghum extracts. The

results of the research conducted in recent years has revealed that one-

third or half dose of herbicides combined with sunflower extracts provide

similar weed control to the labeled (full) dose of herbicides in different

field crops (Cheema et al., 2003a, b, c; Iqbal et al., 2009). Although

successful results have been obtained from sorghum extracts applied with

low herbicide rates, additional work in other soil types and locations

should be performed. In addition, to employ this technology on large

scale operations, large volumes of sprays are required for field

application, and therefore appropriate concentrations for each crop should

be determined.

Due to these limitations, an alternative practical and feasible

approach has been developed for weed management, where low doses of

herbicides are applied along with the residues of allelopathic crops. The

residues of allelopathic crops were left after harvest to dry then

incorporated into field soil during tilling process (Alsaadawi et al.,

2013). By using this approach with sunflower and sorghum, it was found

that a combination of herbicide with sunflower or sorghum residues

resulted in a significant reduction in weed number and biomass as was

achieved by the label dose of herbicide )Alsaadawi et al., 2011; Lahmod,

2012). However, the effects of this combination on beneficial

microorganisms such as mycorrhiza, rhizobia and others could not be

excluded.

Customarily, farmers in Iraq cultivate wheat after sunflower harvest

during October. Several types of herbicides are generally used to control

weeds of wheat. Therefore, it was contemplated in the present studies to:

1. Evaluate the effect of allelopathic residues alone or in

combination with lower (one half of label dose) chevalier dose

on weed population and growth.

2. Test the effect of the above aforementioned combinations on

yield and yield components of wheat crop.

3. To test if the residues of sunflower and reduced chevalier

herbicide alone or in combination with each affect number of

spores, colonization rate and intensity of mycorrhiza associated

with at roots of wheat.

Chapter One

Literature Review

CHAPTER ONE

1. Literatures review

1.1. Allelopathy of crop on weeds

Weed management effects has been a serious problem for

many world countries. Worldwide, a 10% loss of agricultural

products can be attributed to competitive and allelopathic effects

of weeds, despite their intensive control (yarnia, 2011). Potential

yield reductions caused by uncontrolled weed growth throughout

growing season have been estimated to be 45 to 95%, depending

on crop species, weed species, weed densities and ecological

factors (Ampong-Nyarko and De Datta, 1991). Therefore, weed

management is a key element of most agricultural systems.

Although there are various methods to weed control including

cultural, mechanical and biological methods, nevertheless,

application of herbicides has been a major chemical factor

enabling the intensification of agriculture in past decades

(Abdollahi and Ghadiri, 2004). Indeed, three million tones of

herbicides per year are used in most agricultural systems

(Stephenson, 2000). There has been increasing herbicide

resistance in weeds and widespread concern about adverse

environmental effects from herbicide use (Stephenson, 2000). For

this reason, searching of alternative method becomes viable option

to reduce the rely on herbicides. In recent years allelopathy may

provide an alternative to minimize the risk of herbicides towards

agroecosystems.

Several strategies in which allelopathy can play a beneficial

role in cropping systems have been adopted including mixed

cropping, multiple cropping, cover cropping and mulches,

incorporation of crop residues, crop rotations, minimum and no–

tillage systems and using of allelopathic water extracts. Of all

these strategies, utilization of crop residues is the most successful

one (An et al., 1996). In this section, The application of water

extract and residues of allelopathic crops alone or in combination

with low recommended dose of herbicides on weeds and crops are

reviewed.

1.1.1. Effect of allelopathic plant extracts

In the earlier research work on allelopathy, the biological

activities of extract was performed to examine if the allelopathic

crop has phytotoxins which may be responsible for the

allelopathic activity of the tested plant ( Rice , 1984). Later, the

use of allelopathic crops extract has been developed as one of the

strategies used for weed control (Khaliq et al., 2002).

The effect of allelopathic crops extract on weeds has been

also studied under field conditions. Javid et al. (2006) evaluated

the allelopathic potential of aqueous root and shoot extracts of

sunflower, sorghum and rice (Oryza sativa L.) on germination and

growth of the noxious alien weed Parthenium hysterophorus L.

using petri dishes technique . Aqueous root and shoot extracts (5,

10, 15, 20 and 25% (w/v) ) of fresh plant materials of the tested

crops insignificantly affected shoot length and seedling biomass

while germination and root length were significantly reduced by

extracts of all the test crops. In a foliar spray bioassay, when

aqueous shoot extracts at 50 and 100% w/v (on a fresh weight

basis) of sunflower and sorghum were applied on 10 day old

Parthenium plants, the root biomass of Parthenium plants was

significantly suppressed. Both concentrations of sorghum extracts

significantly reduced shoot biomass, but sunflower extract was

inhibitory by the lower concentration only.

Sunflower leaf extracts successfully killed Chenopodium

album and Rumex dentatus weeds in wheat crop and thereby

increased wheat yield significantly (Anjam and Bajwa, 2007).

They suggested that the considerable allelopathic potential of

sunflower could be used as natural herbicide.

Cheema et al. (2008) conducted a series of field

experiments to test allelopathic effects of this crop on weed

control and yield of wheat. They found that 10% w/v water

leachate of aerial parts of sorghum (also called sorgaab) applied at

30 and 60 days after sowing can reduce weed biomass by as much

as 49% with concomitant increase of wheat yield over 20%

compared to the control. They concluded that sorgaab has a great

potential in increasing weed control and grain yield of wheat.

Application of this method of weed management has enormous

economic and environmental benefits in wheat cultivation.

Naseem et al. (2009) studied the allelopathic influence of

sunflower plant water extract (1:10 w/v) on weeds in wheat crop

under field conditions. Results indicated that the highest inhibitory

effects on germination of Phalaris minor was achieved by pre-

emergence application, whereas wheat remained unaffected by

this treatment. Application of water extract at pre-emergence + 25

DAS, 25 + 35 DAS and pre-emergence + 25 + 35 DAS

suppressed growth of Phalaris minor Retz., Chenopodium album

L., Coronopus didymus L. and Avena fatua L.. The inhibitory

effects were species specific and increased with increasing the

water extract application frequency. All the treatments except pre-

emergence + 25 + 35 DAS increased the wheat yield significantly

over control.

Hozayn et al. (2011) conducted field experiment to determine the

response of lentil and its weeds to foliar application of different

concentrations of sorghum or sunflower water extracts. Both sorghum

and sunflower extracts significantly reduced the weeds dry weight by

65.62% and 63.56% and thus increased the lentil dry weight by 67.66%

and 64.41% over the control and the lentil seed yield by 61.34% and

56.18% of control, respectively.

Nikneshan et al. (2011) evaluated the allelopathic potential

of different concentrations (25, 50 and 100% w/v) of sunflower

cultivars on several crops and associated weeds. Results showed

that Amaranthus retroflexus was the most sensitive to sunflower

allelopathy and Portulaca oleracea was the most resistant. As

extract concentration increased from 25 to 100%, the inhibitory

effect on germination indices increased, while with 25% extract

concentration was observed to have stimulatory effects on wheat

and P. oleracea germination. The Megasun sunflower cultivar had

the most effect and Hysun 36 had the least effect on the target

plants. Megasun extract at 100% concentration suppressed

selected weeds by 80%. The results also indicated that the

allelopathic properties of some sunflower cultivars can affect

noxious weed species such as Hordeum spontaneum and Lolium

rigidum in wheat and A. retroflexus in safflower crop.

Awan et al. (2012) tested the allelopathic effect of different

combinations of water extracts of sorghum, sunflower and

brassica on weeds in wheat crop under field conditions. Extracts

were prepared by soaking chopped dry sorghum, sunflower and

brassica herbage separately in water for one day in the proportion

of 1:10 (w/v). The treatments were control, hand weeding, foliar

application of sorghum, sunflower and brassica individually and

combined as sorghum + sunflower, sorghum + brassica, sunflower

+ brassica and sorghum + sunflower + brassica. Results revealed

that the highest weed density and biomass suppression was

achieved by hand weeding. Among the foliar application of

extracts, the highest weed control was recorded with the combined

application of concentrated aqueous extracts of sorghum,

sunflower and brassica at 45 and 75 days after sowing followed by

sorghum + sunflower extracts. The highest increase of yield and

yield components of wheat was recorded by manual weeding and

the lowest by control. Among extracts application treatments, the

highest increase in wheat biomass and yield attributes was found

by combined application of sorghum, sunflower and brassica

extracts compared to rest of the treatments.

Khan and Khan (2012) conducted a field experiment

during spring of 2010 to test pre and post application of plants

extract for weed control and their impact on grain yield of wheat.

Water extracts of sorghum, sunflower, Parthenium, (Phragmites

australis L., Johnson grass (Sorghum halepense) and rice extract,

herbicide (Logran Extra 64 WG), and a weedy check. They found

that pre-emergence application of plant water extracts proved to

be superior than post-emergence application in controlling weeds.

Pre-emergence application of P. australis and sunflower gave 68

and 65% reduction in weed control, respectively. Sorghum gave

maximum grain yield 5015 kg ha-1

in comparison to weedy check

2700.6 kg ha-1

. The instant results suggest that P. australis, H.

annuus and sorghum extracts could be successfully incorporated

in weed management approaches in wheat.

The allelopathic effect of sunflower extract on weeds was also

studied under laboratory conditions (Ghafar et al., 2000; Batlang et al.,

2007; Mubeen et al., 2012; Azadbackht et al., 2013; Khaliq et al.,

2013). In most of these studies, suppression of test weeds and crops has

been observed, particularly at the higher concentrations of the extracts.

1.1.2. Effects of allelopathic crop residues

Allelopathic crops residue decomposition produces a variety

of phytotoxins in the soil causing adverse effects on other plants

(Nelson, 1996), and have the potential to sustain a chemical as

well as physical effect on the growth and development of

subsequent crops and weeds (Reddy, 2001). Allelopathic crop

residues can be exploited for weed suppression, and can thus be

helpful in reducing reliance on herbicides (Weston, 1996). In this

section, the potential role of allelopathic crop residues in weed

management is briefly reviewed.

Putnam and DeFrank in 1983 found that the populations of

Portulaca oleracea L. and Digitaria ischaemum L. (Schreb) were

reduced by 70% and 90% by residues of sorghum, respectively. In

general, the larger-seeded vegetables, particularly legumes grew

normally or were sometimes stimulated by the residues, whereas

several species of smaller-seeded vegetables were severely

injured. Glasshouse experiments with two soils confirmed both

weed-suppressing and crop-stimulating effects of sorghum

residues.

In Pakistan, Cheema and Khaliq (2000) found in a field experiment

that incorporation of whole sorghum plant or its various parts alone or

mixed with each other suppressed total weed dry weight from 26-56%

and increased wheat yield from 6-17% over weedy check.

Srisa-ard (2007) investigated the effects of residues of sunflower,

maize (Zea mays L.) and soybean (Glycine max L) on total dry weight,

top dry weight, plant height, root dry weight and seed yield of sunflower

plants using Koral soil series (Oxic paleustults) during the rainy season

(July-october) of the 2001. Whilst crop residues of roots, top growth and

roots top growth were used as subplots. The results showed that crop

residues derived from roots of both sunflower and soybean plants

significantly inhibited plant height, root dry weight, top growth dry

weight and total dry weight plant of the sunflower plants compared to

those derived from top growth of both crops alone (sunflower and

soybean). Maize plant residues had no significant inhibitory effect on

growth of subsequent sunflower crop.

In Iraq, several hundreds of sorghum cultivars were introduced and

cultivated to select the most promising genotypes in terms of production,

weed competition, and fitness to local environment. Field observation by

Alsaadawi et al. (2007) revealed that growth and population of

companion weeds were variable among stands of selected genotypes.

Additional work indicated that residues of all test cultivars significantly

inhibited the growth of Lolium temulentum weed. The phytotoxicity of

residues differed among the test genotypes. Experiment conducted in

afield infested with Lolium rigidum, L. temulentum, Malva pariflora,

Carthumus oxycantha, Chenopodium album, Beta vulgaris, Trifolium

repense and Plantago ovate revealed that the aboveground biomass and

number of all weeds were reduced by the residues of test sorghum

cultivars incorporated into field soil at rates of 3 and 6 g/ kg soil.

However, the response varied among the weed species. Residues of

cultivars Giza 15, Giza 115 and Enkath provided 67, 59, and 63%

reduction in average weed number and 58, 66, and 58% reduction in

average weed biomass, respectively. Residues of Rabeh cultivars

inhibited average weed numbers and average weed biomass by 41 and

52%, respectively. Weeds numbers were significantly decreased with

increasing rate of residues of the stronger allelopathic cultivars in soil.

The phytotoxicity of the residues started after 1 week of decomposition

and persisted for 8 weeks at low rate of residues and for 10 weeks at the

higher rate of residues. The reduction was proportional to the amount of

residues in soil during the first 6 weeks of decomposition. Giza 15, Giza

115, and Enkath showed greater phytotoxicity than Rabeh cultivar at all

decomposition periods.

Ashrafi et al. (2008) conducted greenhouse and laboratory

experiments to determine the effects of sunflower residues on

germination and seedling growth of wild barley (Hordeum spontaneum

Koch.). They showed that incorporation of fresh roots of sunflower alone

or in combination with shoots significantly reduced wild barley

germination, plant height and weight as compared with control (no

residue). Laboratory experiment revealed that the degree of toxicity of

different sunflower plant parts showed the following order of inhibition:

leaves > flowers > mixture of all plant parts > stems > roots.

Khaliq et al. (2010) conducted field experiment to test the

weed suppression potential of mixture of allelopathic crop

residues and their effects on maize yield. Residues of sorghum,

sunflower, rice and brassica (Brassica campestris L.) in various

combinations were incorporated in soil at 5 and 7.5 t ha-1

.

Results revealed that a combination of sorghum + sunflower +

brassica residues at 7.5 t ha-1

provided > 90% suppression in

density and dry weight of horse purslane (Trianthema

potrtulacastrum L.) and purple nutsedge (Cyperus rotundus L.) as

compared with control (no residue). This treatment also accounted

for maximum maize grain yield and net benefits. They concluded

that for better management of natural resources and to decrease

environmental pollution, soil incorporation of crop residues may

serve as an important weed management tool in maize fields.

Matloob et al. (2010) evaluated allelopathic potential of different

crop residues viz. sorghum, sunflower, brassica (applied alone or in

combination) for the purple nutsedge suppression in a pot study. Chopped

residues were incorporated at 12 t ha-1

(6 g kg-1

of the soil) into the soil

and a weedy check was also maintained. There were six tubers of purple

nutsedge in each soil filled pot. Soil incorporation of all the residues

substantially delayed the tuber sprouting. Nonetheless combinations of

residues showed more effective in purple nutsedge suppression than sole

application of either of them. Sorghum and brassica residues, when

applied in combination did not allow any tuber to sprout. There was

substantial suppression in final germination by 41- 45% from sole

application and 27-100% from combination of crop residues. These

residues exerted a pronounced negative influence on the shoot and root

length by 21-100 and 17- 100%, respectively. Likewise, there was 50-

100% and 47-100% suppression in shoot and root dry weights,

respectively. Hence, soil incorporation of the test allelopathic crop

residues may be employed in the integrated approach for purple nutsedge

management.

Khaliq et al.(2011) evaluated the allelopathic potential of different

of residues of sorghum, sunflower and brassica on rice crop and jungle

rice weed (Echinochloa coloma [L.] Link). Soil incorporation of residues

substantially delayed germination of jungle rice. The time to start

germination, time to 50% emergence, mean emergence time, emergence

index and final germination percentage were all depressed by residue

incorporation. Final germination of rice and jungle rice dropped by 11 to

15% and 11 to 27% with residue application alone and by 18 to 22% and

8 to 34% with a combination of crop residues, respectively. Residues

were more suppressive to germination dynamics of jungle rice than rice.

Crop residues exerted a pronounced negative influence on the shoot (25

to 100% and 14 to 44%) and root lengths (22 to 100% and 10 to 43%) of

rice and jungle rice, respectively. Shoot and root dry weight of both rice

and jungle rice were also decreased significantly. An appreciable

quantity of phenolics was recorded in soil amended with sorghum +

sunflower + brassica residues. They suggested that the time of residue

application for jungle rice suppression and rice seeding time need to be

adjusted to minimize rice crop damage.

Alsaadawi et al. (2011b) evaluated eight genotypes of sunflower for

their allelopathic potential against weeds and wheat crop which is

customarily grown after sunflower in crop rotation in Iraq. They are

revealed that all sunflower genotypes significantly inhibited total number

and biomass of companion weeds and the magnitude of inhibition is

genotype dependent. Of the 8 genotypes tested Sin- Altheeb and Coupan,

were the most allelopathic potential cultivars with the reduction in total

weed number by 47.25 and 86.81 % of control and weed biomass by

74.23 and 80.79% of the control respectively. Euroflor and Shumoos

were the least allelopathic potential genotypes with an inhibition in total

weed number by 21.50 and 9.59% and weed biomass by 42.28 and

33.67% of the control respectively. Subsequent field experiment indicated

that the residues of sunflower incorporated into the field soil significantly

inhibited total number of weeds grown in wheat field by 24.51-74.52% of

control at low residues rate (3g kg-1

soil) and by 49.05-75.47% at the

high residues rate (7g kg-1

soil). Weeds biomass significantly reduced

with a range of 12.27-64.52% at low residue rate and 40.33-66.75% at

high residue rate. However, sunflower genotypes Sin Altheeb and

Coupan appeared to be more inhibitory to total weeds number and

biomass and significantly increased yield of wheat compared to the least

allelopathic potential genotypes (Euroflor and Shumoos genotypes).

Chromatographic analyses by HPLC revealed the presence of 13

phytotoxins in the residues of the tested sunflower genotypes. All the

isolated compounds appeared to have different retention times and were

identified as phenolic compounds with the exception of terpinol which is

known as terpenoid derivative. The total concentration of phytotoxins

appeared to be dramatically increased in the most allelopathic potential

genotypes compared to the least allelopathic potential genotypes.

Alsaadawi et al. (2014) tested if the variation in weed

population and biomass between the stands of Enkath and Rabeh

sorghum cultivars, which was observed in the field, was due to

differences in their allelopathic potential. Field experiment

revealed that Enkath cultivar significantly suppressed weed

density and dry weight biomass over Rabeh cultivar by 34 and

29% of control after 35 DAS, and 22 and 24% after 65 DAS. Stair

case experiment indicated that root exudates of Enkath cultivar

showed more suppression to weeds than Rabeh giving additional

evidence for the superiority of Enkath cultivar in its allelopathic

weed suppression. Chemical analysis revealed that sorgoleone and

several phenolic acids were present in higher concentrations in

root exudates of Enkath compared to Rabeh. Thus it appears that

the variation in weed suppressive ability between the test sorghum

cultivars was attributed to their differences in allelopathic

potential of root exudates and the phytotoxicity of root exudates

was not restricted to sorgoleone alone but with phenolic acids.

The results recommend screening more sorghum cultivars in order

to offer a potential source of allelopathic germplasm that could be

manipulated to enhance weed suppression in an effective and

environmentally sustainable approach.

1.1.3. Combined effect of allelopathic extract with

herbicides

As in sections 1.1.1 and 1.1.2 the allelopathic extracts or crop

residues provide limited weed suppression, and most often reductions in

weed growth are not comparable to those observed with labeled

herbicides. Therefore, other methods to increase the efficacy of

allelopathic extracts may be critical to enhance weed suppression while at

the same time reducing our reliance on herbicides. Furthermore it has

been reported that allelochemicals and herbicides work in concert to

inhibit the growth of weeds, e.g. adequate allelopathic crop plus reduced

input of herbicide give adequate weed control (Einhellig and Leather,

1988; Einhellig, 1995, 1996; Streibig et al., 1999). In this section, the use

of integration of allelopathic extracts and lower dose of herbicide is

reviewed.

Mahmood et al. (2009) indicated that combined application of

sorghum water extract (sorgaab) and sunflower water extract (sunfaab)

each @ 15 L ha-1

with 1/3rd

of the label dose of phenoxoprop-p-ethyl

showed maximum weed suppression at 45 and 65 days of sowing of

wheat. Bromoxinil + MCPA alone did not show effective weed control at

lower rates. Sorgaab and sunfaab 15 L ha-1

each in combination with 1/3rd

dose of phenoxoprop p-ethyl resulted in maximum grain yield and net

benefits, but bromixinil + MCPA alone was effective only at higher rates.

Increase in yield was only due to effective weed control and

improvements in yield components of wheat crop.

Khan et al. (2009) conducted a field trial to investigate the

response of sunflower and its weeds to sorghum water extract

(sorgaab) in combination with reduced doses of Dual gold

herbicide. Results revealed that Sorgaab @ 15 L ha-1

+ 1/3rd

dose

of Dual gold reduced Chenopodium album density by 92% at 70

DAS. Sorgaab alone @ 15 L ha-1

, full dose reduced Chenopodium

album density by 81% at 70 DAS. Sorgaab + 1/3rd

dose of Dual

gold reduced Coronopus didymus density by 68%. While Sorgaab

alone @ 15 L ha-1

, decreased C. didymus density by 36%. Sorgaab

+1/3rd

dose of Dual gold, decreased total weed density by 89%,

over control at 70 DAS. While Sorgaab alone @ 15 L ha-1

reduced

weed density by 76% at 70 DAS. Total dry weed biomass

suppressed by sorgaab + Dual gold, 1/3 rd

dose was 92% at 70

DAS. While sorgaab alone @ 15 L ha-1

reduced total dry weed

biomass by 85% at 70 DAS. It was also observed during this study

that plant height, head diameter, stem diameter, number of

achenes per head, 1000-achene weight and achene yield were

significantly affected by the combination of sorgaab 15 L ha-1

, full

dose and 1/3rd

dose of Dual gold herbicide.

Cheema et al. (2010) conducted a field trial to determine the

effect of allelopathic water extracts (sorghum + sunflower, and rice husk)

alone or in combination with lower rates of penoxsulam (Ryzelan). The

mixture of sorghum + sunflower @ 18 L ha-1

suppressed the density of

different weeds (up to 50%) and dry weight (up to 49%) while rice husk

@ 18 L ha-1

suppressed the density (up to 46%) and dry weight of weeds

(up to 49%). The water extracts with half dose of herbicide were effective

in controlling weeds and their effectiveness was equal to full dose of

herbicide at 20 and 40 DAS, while at 60 DAS, they provided good

control of weeds but not equal to the full dose of herbicide. The mixtures

of water extracts with 1/3rd

dose of herbicide were less effective in

reducing the weed density and dry weight of weeds as compared to

mixture of water extracts with half dose of herbicide. However, full dose

of penoxsulam was the most effective treatment in reducing the weed

density and dry weight of the weeds.

Jabran et al. (2010) found that when water extracts of sorghum

sunflower, mustard and rice each at 15 L ha-1

were tank mixed with 0.4

and 0.6 kg active ingredient (a.i.) ha-1

pendimethalin and sprayed

immediately after sowing of canola (Brassica napus L.), density, fresh

weight and dry weight of weeds were lower than that of control in all the

treatments; however the performance of various combinations of

allelopathic crop water extracts and lower pendimathalin rates was better

than the standard dose of herbicide particularly in case of purple

nutsedge. All yield parameters including number of branches per plant,

number of pods per plant, numbers of seeds per pod and 1000-seed

weight were higher, when combinations of allelopathic extracts were used

with lower herbicide rates.

Razzaq et al. (2010) tested the allelopathic crop water extracts

with reduced herbicide doses for weed management in wheat. Sorghum

and sunflower water extracts combinations each at 18 L ha-1

with reduced

doses of 70% of mesosulfuron + idosulfuron (Atlantis 3.6 WG),

mesosulfuron + idosulfuron (Atlantis 12 EC), metribuzin + fenoxaprop

(Bullet 38 SC), bensulfuron + isoproturon (Cleaner 70 WP) and

metribuzin (Sencor 70 WP) were compared with their label doses which

were sprayed alone 30 days after sowing for weed control in wheat.

Combination of sorghum + sunflower each at 18 L ha-1

with reduced dose

of metribuzin + fenoxaprop significantly reduced dry weed biomass by

92% compared to label dose of mesosulfuron + idosulfuron (93%).

Treatment combination of sorghum + sunflower each at 18 L ha-1

with

reduced dose of metribuzin + fenoxaprop by 70% produced maximum

(2.82 t ha-1

) grain yield with 34 % increase over control and it was

significantly higher by 17% than its label dose .

Rehman et al. (2010) revealed that combined application of

mixture of allelopathic crops water extracts of sorghum, sunflower and

rice with ½ of the recommended dose of pre-emergence herbicides

butachlor (600 g a.i. ha-1

), pretilachlor (313 g a.i. ha-1

) and

ethoxysulfuronethyl (15 g a.i. ha-1

) reduced barnyard grass (Echinochloa

crusgalli L.), flat sedge (Carex spicata L.) and crowfoot grass

(Dactyloctenium aegyptium L.) density by 75, 67 and 74% and their dry

weight by 66, 71 and 76%, respectively, while 1/3rd

of the recommended

dose of butachlor (400 g a.i. ha-1

), pretilachlor (208 g a.i. ha-1

) and

ethoxysulfuronethyl (10 g a.i. ha-1

) in combination with mixture of

allelopathic water extracts reduced the density and dry weight of these

weeds by 68, 60 and 67% and 63, 67 and 72%, respectively. Application

of water extracts mixture with ½ of the label rates of pre-emergence

herbicides improved rice grain yield by 61, 59 and 41%, respectively,

while mixture of allelopathic extracts alone enhanced rice grain yield by

29% over control.

Iqbal et al. (2010) carried out afield trial to investigate the

response of wheat crop and its weeds to various crop water

extracts sorghum, brassica and sunflower in combination with

reduced rates of herbicide (Bromoxynil + MCPA 20 + 20 EC).

The data recorded at 70 DAS (days after sowing) showed that

water extracts @ 18 L ha-1

combined with Bromoxynil + MCPA

50 g a.i ha-1

inhibited total weeds density by 88%, total weeds

fresh weight by 90% and total weeds dry biomass by 95% and

increased grain yield by 35% over control.

Razzaq et al. (2012) indicated that spraying of sorghum + sunflower

extract each at 18 L ha-1

combined with 70% reduced dose of

mesosulfuron + idosulfuron or metribuzin + phenoxaprop or

mesosulfuron + idosulfuron reduced total weed dry weight by more than

90% over the control. On the other hand, sorghum and sunflower water

extracts each at 18 L ha-1

combined with metribuzin + phenoxaprop

produced a maximum number of productive tillers, spikelet's per spike,

number of grains per spike, biological yield and grain yield.

Khan et al. (2012) investigated the possible effects of allelopathic

plant water extracts of sorghum, brassica, sunflower and mulberry in

combination with reduced doses of atrazine for weed control in maize.

The four levels (full, ½,⅓ and ¼ dose) of atrazine showed 65-81%

suppression of weeds density and weeds dry weight over control (weedy

check), while allelopathic plant water extracts showed 70-75%

suppression of weeds density and dry weight when used in combination

with half and 1/3rd

dose of atrazine over control. Nonetheless, 49%, 36%

and 31% more grain yield was obtained when full dose (alone) and half

and ⅓rd

dose of atrazine in combination of allelopathic plant water extract

was applied, respectively.

1.1.4. Combined effect of allelopathic residues with

herbicides

Although successful results have been obtained from crop extracts

applied with low herbicide rates, additional work in other soil types and

locations should be performed. To employ this technology, large volumes

of sprays are required for field application, and therefore appropriate

concentrations for each crop should be determined for large scale field

operations. Due to these limitations, an alternative practical and feasible

approach has been developed where the residues of allelopathic crops

including sorghum have been left to dry under field conditions and then

promptly incorporated into production sites for weed management (Al-

Bedairy, 2011). In this section, a review will be made to include all the

activities which have been done on this approach.

Alsaadawi et al. (2011a) conducted field trial with the aim of

utilizing allelopathic crop residues to reduce the use of synthetic

herbicides in broad bean (Vicia faba) fields. They found that a

combination of trifluralin herbicide with sunflower residue had the least

total count and biomass of weeds in broad bean, which was even better

than herbicide used alone. Integration of recommended dose of trifluralin

with sunflower residue at 1400 g m-2

produced maximum (987.5 g m-2

)

aboveground biomass of broad bean, which was 74 and 36% higher than

control and recommended herbicide dose applied alone, respectively.

Combination of herbicide and sunflower residue appeared to better

enhance pod number and yield per unit area than herbicide alone.

Application of 50% dose of trifluralin in plots amended with sunflower

residue resulted in similar yield advantage as was noticed with 100%

herbicide dose. Chromatographic analysis revealed the presence of

several phenolic compounds in the soil containing sunflower

residues and none of these appeared in soil without sunflower

residues. Concentration of total phenolic compounds appeared to be

increased at two weeks of decomposition, reached its maximum at

the 4th

week of decomposition and started to decline thereafter until

vanished at the 8th week of decomposition. Weeds population started to

increase after 6 weeks of residues decomposition when the phytotoxins

concentration was sharply reduced in the soil.

Alsaadawi and Al-Temimi (2011) evaluated the allelopathic

potential of sunflower residues alone and in combination with

subrecommended doses of 2,4-D and Topic herbicides against weeds of

barley crop. Results revealed that combination of recommended dose of

herbicides with sunflower residues at 1400 g m-2

produced minimum

above-ground biomass (122 g m-2

) and weeds number (155.5 weeds per

m2 ), which were 35 and 50% less than recommended herbicide dose

applied alone, respectively. Meanwhile, integration of herbicides and

sunflower residue appeared superior in enhancing yield per unit area than

herbicide alone. Application of 50% dose of herbicides on plants growing

in plots containing sunflower residues at 1400 g m-2

resulted in similar

yield advantage as was noticed with 100% herbicide dose.

Alsaadawi et al. (2013) conducted two year field study to explore

the response of broad bean crop and its weeds to soil incorporated

allelopathic sorghum residues in combination with lower rate of a pre-

plant herbicide (trifluralin). Results indicated that plots treated with 50%

of label rate of herbicide and amended with sorghum residues recorded

least weed density and dry biomass and this suppression was much

greater than the residue treatments alone. Application of herbicide at 50%

rate in plots amended with sorghum residue resulted in similar yield as

with the 100% herbicide rate treatment. Chromatographic analysis of

sorghum amended field soil revealed the presence of several potent

allelopathic compounds of phenolics in nature. Periodic data revealed that

maximum quantities of these phytotoxins were coincided with the period

in which maximum suppressive activity against weeds was noticed under

field condition, which explain the activity of phytotoxins on weed

suppression. They suggested that integration of sorghum residues with a

lower herbicide rate can furnish adequate weed suppression without

compromising yield, which could be used as a feasible and

environmentally sound weed management approach in broad bean fields.

Lahmod and Alsaadawi (2014) conducted A two-year field trial to

test the response of wheat crop and its weeds to different rates of

sorghum residues alone or in combination with 50% of the label rate of

Chevalier herbicide. Results showed that all treatments significantly

reduced weed population and dry weight of weeds in comparison to

weedy check treatments during both years of the study. However, plots

treated with 50% of label rate of herbicide and amended with sorghum

residues recorded least weed density and dry biomass and this

suppression was much greater than the residue treatments alone.

Application of chevalier herbicide at 50% rate in plots amended with

sorghum residue at rates 3.50 and resulted in similar yield as with the

100% herbicide rate treatment. The increase in yield apparently due to

increase number of grains and weight of grains over control. They

concluded that integration of sorghum residues with a lower herbicide

rate can furnish adequate weed suppression without compromising yield.

1.2. Effect of phenolic compounds on arbuscular mycorrhiza

Cooper (2004) mentioned that some phenolic compounds are

important signal molecules for the development and growth of both plants

and microbes. During the arbuscular mycorrhiza fungi (AMF)

colonization. The effects of phenolic compounds on spore germination

and the subsequent colonization have been intensively investigated

(Becard et al., 1992; Gianinazzi and Gianinazzi-pearson, 1992). Factors

inducing the germination of AMF spores and the following a symbiotic

growth of germ tube have been determined including soil-derived stimuli

(e.g. CO2, ethylene) and plant-derived signals (e.g. phenolic compounds)

(Nair et al., 1991). Nagahashi et al. (1996) compared the phenolic

constituents in cell walls and cytoplasm's of host (carrot) and non-host

(sugar beet) of AMF, and observed some phenolic acids unique to host

while others unique to non host. In further bioassay, they demonstrated

that phenolic constituents in host roots were not always stimulatory and

those in non host roots were not always inhibitory to the growth of AMF

(Douds et al., 1996).

Some plant phenolic compounds have been found to be potential

candidates as signals during mycorrhizal formation. Some reports show

that exogenous application of flavonoids exerts a positive effect on

hyphal growth during symbiosis (Gianinazzi-Pearson, 1989; Tsai and

Phillips, 1991; Poulin et al., 1997). These effects range from increased

spore germination to enhanced hyphal growth, hyphal branching and

formation of secondary spores. It has been shown that the arbuscular

mycorrhizal formation alters the flavonoid profile of root extracts through

modifications to the expression of genes involved in phenylpropanoid,

flavonoid and isoflavonoid metabolism (Harrison and Dixon, 1993;1994).

Flavonoids are specific to mycorrhizal symbiosis formation, a single

flavonoid might exert a positive, negative or neutral effect on different

fungi (Siqueira et al., 1991a; Poulin et al., 1997). This may be explained

by specific effects of each flavonoid, as recently reported (Scervino et al.,

2005). Therefore it is likely that the role of flavonoids is limited to a

stimulatory effect on AM fungal growth (Silva-Junior and Siqueira,

1998).

Among a large variety of phenolic compounds, those stimulatory or

inhibitory to AMF spore germination have been described. Chabot et al.

1992 reported that at 2% CO2 conditions, flavonols (Kaempferol,

quercetin and morin) with at least one hydroxyl group on the B ring

improved spore germination and hyphal growth of G. margarita, while

biochanin A, genistein, hesperetin, galangin and chrysin inhibited the

hyphal growth. The latter two compounds possess no hydroxyl group on

the B ring. Buee et al. (2000) have reported a root factor (one or several

molecules) that stimulated the nuclear division and thus improved the

hyphal branching of G. gigantean germ tube. They demonstrate the

presence of this active factor in root exudates of all mycotrophic plant

species tested (eight species) but not in those of nonhost plant species

(four species), and further they hypothesized that this lipophilic

compound was not a flavonoid or a compound synthesized via the

flavonoid pathway. This hypothesis is consistent with the results of

Becard et al. (1995) who stated that root metabolites in addition to

flavonoids may stimulate AM fungal growth. Recently, Akiyama et al.

(2005) isolated a branching factor from the root exudates of Lotus

japanicus and further identified it as sesquiterpene. They found that

natural strigolactones, 5-deoxy-strigol, sorgolactone, strigol sythetic and

strigolactone analog GR24 induced extensive hyphal branching in

germinating spores of Gigaspora margarita at concentration as low as 3-

10 pg per disk.

Several workers have observed considerable increases in phenolic

compounds in the host as a result of AMF inoculation (Ling-lee and

Chilvers 1977; Selvaray and Subramanian, 1990). Giovannetti et

al.(1996) speculated that only the perception of the right chemical signals,

coming from the roots of host plants, promotes differential

morphogenesis of AMF hyphae in the rhizosphere and that root cells

penetration by the fungus depends on the host genome. Therefore,

phenolic compounds could enhance the initial stages of AMF

establishment, but root penetration and AMF development are likely

regulated by the host plant and subsequent interactions with the fungal

partner.

The effects of the application of 0.25 or 1.0 mM p-coumaric acid,

p-hydroxybenzoic acid, or quercetin on growth and colonization of clover

(Trifolium repens L. cv. Ladino) and sorghum (Sorghum bicolor L.) roots

by the arbuscular mycorrhizal (AM) fungus Glomus intraradices were

studied (Schenck and Smith, 1982). In general, soil application of these

compounds at 0.25 mM stimulated plant growth and AMF colonization,

whereas at 1.0 mM these phenolics were inhibitory to both growth and

colonization. Such effects were noted for both clover and sorghum. The

results suggest that phenolic compounds, commonly found in many soils,

influence the establishment of AMF symbioses, and these compounds

may have immediate effects on host growth. They indicated that studies

involving these chemicals and their effects on mycorrhizal associations

may provide new insights concerning the importance of the AMF

symbiosis in agricultural systems. These phenolic compounds may be

used as potential soil amendments to enhance AM fungal colonization,

and thus, exploit indigenous populations of AM fungi (Fries et al., 1997).

In another study, Martin et al, (2002) also mentioned that among

the various phenolic compounds, flavonoids are the most intensively

studied in AMF colonization. They revealed that the effects of flavonoids

on the AMF colonization are stimulatory, null and even inhibitory,

depending on the molecular species and concentration.

Siqueira et al. (1991a) studied the effects of flavonoid compounds

on VA (AM) mycorrhiza root colonization and growth of white clover

(Trifolium repens L.) plants under growth chamber conditions. The

isoflavonoids, formononetin and biochanin A, previously identified from

clover roots, stimulated colonization and growth of clover, while several

other flavonoid compounds were inactive when tested at concentrations

of 5 mg 1−1

. The flavone, chrysin, when applied at concentrations higher

than those tested for formononetin and biochanin A, also increased root

colonization and plant growth. The stimulatory effects of the

isoflavonoids on plant growth were mediated by VA mycorrhizal fungi

and were dependent on concentration, period of growth and soil spore

density. Maximum responses were found when 5 mg 1−1

solutions were

applied to soil containing 2 to 4 VA mycorrhiza spores g−1

of soil. These

results may provide insights on the molecular mechanisms of host-fungus

interaction and for the development of technology to exploit the potential

of the indigenous VA mycorrhizal fungi in field soil. They also suggested

that the stimulatory effects of these compounds on colonization were

mediated by concentration, because flavones and chrysin increased root

colonization and plant growth at the concentration above 5 mg l-1

. Caffeic

acid showed a stimulatory effect on hyphal mycorrhizal colonization at

5×10-5

M, but it produced an inhibitory effect at 5×10-4

and 5×10-3

M.

(Siqueira et al. 1991b).

The effects of an aqueous extract of Artemisia princeps var.

orientalis and two phenolic compounds on mycorrhizal colonization and

plant growth have been investigated (Yun and Choi., 2002). Under

greenhouse studies, they showed that the inhibitory effect of the extract

on mycorrhizal colonization and plant growth increased in proportion to

the concentration of the extract. When the mycorrhizal test plants were

treated with an increasing concentration of phenolic compounds, the

mycorrhizal colonization in roots of the test plant and the plant growth

were decreased. There were strong indications that mycorrhizal fungi

mitigated the inhibitory influence of shoot extract of A. princeps var.

orientalis and phenolic compounds.

In contrast, the reduced colonization due to the application of

phenolic compounds has also been reported. Olive mill residue normally

contains phenolic compounds of 15 mg kg-1

. When AMF inoculation was

done 4 weeks prior to the application of olive mill residue, no effect was

observed on the colonization, whereas the application of AMF

inoculation significantly decreased the colonization (Martin et al., 2002).

This case indicates that phenolic compounds probably exert inhibitory

effects on colonization by suppressing spore germination.

AMF colonization is the function of many factors (spore

germination, growth and branching of germ tube, root exudation, root

signaling). Recent experiments showed that phenolic compounds may

also act as a signaling molecules. With exogenous flavonoids, apigenin

and daidzein. Dong and Zhao (2004) successfully induced the

colonization of non-mycorrhizal plant Brassica juncea Cross by G.

intraradices or G.mosseae. The alkaline phosphatase activity in colonized

roots was observed and new spore were also produced 13 weeks after

treatment. However, they found the effect of flavonoids were

concentration dependent,with 150 nmol l-1

better than 15 or 1500 nmol l-1

.

Vierheilig et al.(2000) indicated that although some phenolic

compounds are stimulatory to AMF colonization, but recent researches

showed that AMF infection inhibited the root colonization in barley

plants by AMF due to effect of phenolic compounds.

Afzal et al. (2000) have reported that the application of aqueous

extracts of Imperata cylindrica, an allelopathic grass, markedly reduced

AMF colocization in Vigna radiate. In a review article by Javaid (2007),

the two allelopathic grasses namely, I. cylindrica and Dichanthium

annulatum have been shown to adversely affect the AMF colonization

extent in the associated weed species. This reduction in AMF

colonization under the allelopathic effects is mediated by an array of

biochemicals released into the soil by plants. These may include phenolic

substances, flavonoids and many more (Siqueira et al. 1991b; Lynn and

Chang, 1990). These phenolic compounds are produced as plant exudates

or as a result of decomposition of plant debris. These biochemicals are

signal transduction molecules and are liable to produce both stimulatory

and inhibitory effects depending upon the concentration (Becard et al.

1992).

Chapter Two

Materials

and

Methods

CHAPTER TWO

2. Materials and Methods

2.1. Field preparations

2.1.1. Site selection

The proposed study was conducted at Research Farm of Biology

Department, College of Science, Baghdad University, Baghdad, Iraq. The

soil of experimental site was calcareous silt clay loam.

2.1.2. Seeds and herbicides sources

Seeds of sunflower cv. Asgrow and grains of wheat cv. Abu Ghraib

were obtained from Department of Crop Sciences, College of

Agriculture, Baghdad University. Chevalier WG herbicide

(Mesosulfuron + Iodosulfuron) which belongs to a group of Sulfonyl-

urea. The herbicide is a product of Bayr Crop Science Company.

2.1.3. Soil Sampling and Analyses

Soil samples were taken at flowering stage from control and treated

(plots amended with sunflower residue at 6 t ha-1

) plots from the wheat

field . Two samples were taken randomly from each plot, 10-15 cm deep.

The samples were mixed, air- dried, sieved through a sieve with 2 mm

openings to remove large rock and plant debris, and pulverized. The

small roots and stones were picked out. Soil texture, organic matter and

electrical conductivity (Ec) , pH , inorganic nutrients NH4, NO3, P, N, Mg

and K were carried out in Ministry of Science and Technology. The

physical and chemical characteristics of the soil were listed .

Table 1. Some Physical and chemical properties of field soil before and

after sunflower residue incorporation.

Values ParM Mmeterss

Parameter Plots amended with

sunflower residues

Control Plots

87.52 88.22 % Sand

68.88 62.73 % Clay

65.83 69.88 % Silt

Clay loam Clay loam Soil texture

5.9 5.3

pH**

8.63 9.92

Electrical

conductivity(dS.m-1

) 1.70 3.53 % Organic carbon

50.34 93.68 NH4+-N ( ppm)

62.53 73.9 NO3--N (ppm)

33.38 4.54 P (ppm)

833.3 883.92 Na (ppm)

353.88 387.33 Mg++

(ppm)

70.12 93.39

K+(ppm)

Each value was an average of 4 replicates. **

In saturated past extract at 25 C

2.1.4. Preparation of sunflower residues

To prepare residues of sunflower plants, field plot (7×2 m) were

tilled twice at the beginning of July 2012. Seeds of sunflower was sown

in 75 cm spaced crop rows with distances of 25 cm between seeds. Plot

(12×2 m) without crop was used as a control. Fertilizers were nitrogen as

urea (46% N) at 240 kg ha-1

and phosphorus as triple super phosphate

(46% P2O5) at 240 kg ha-1

. The whole phosphorus and half of the nitrogen

were applied at planting while the remaining half of the nitrogen was

applied after two months (AL-bedairy, 2011). Irrigation was applied as

recommended for this crop. At physiological maturity, the heads were

removed then 50% of the half sunflower plant parts while, the other half

were left for drying for several days. These plot areas were then tilled

twice at mid November 2012 by using a disc plough to incorporate

sunflower residues in to the soil. Residue free treatment was maintained

as control on an intentionally un-cropped area of the same field. Field

measurements revealed that the residues of sunflower incorporated in

field soil before and after removal half of sunflower plant parts

correspond to sunflower residue rate of about 6 and 3 t ha-1

.

2.2. Field trial

The plots that received sunflower residues at 0, 3 and 6 t ha-1

of

previous experiment were subdivided into plots measuring 2×1.5 m at the

middle of November 2012. Fertilizers Nitrogen as urea (46% N) and

phosphorus as triple super phosphate (46% P2O5) were applied to these

plots as recommended for wheat crop (Cheema and Khaliq, 2000). Each

field plot was treated on lines with 250 g of Arbuscular mycorrhizal

(Glomus mosseae) inoculum (spores, hyphea and roots of the host) before

sown wheat. Grains of wheat cv. Abu-Grab were manually sown in all

plots in 20 cm apart crop rows at seeding rate of 120 kg ha-1

. All plots

received equal irrigation water during the entire course of study. The

experiment consists of the following treatments:

a. Control (un cultivated sunflower field)

b. Residues at 3 t ha-1

c. Residues at 3 t ha-1

+ 50% of label rate of chevalier 15 WG

d. Residues at 6 t ha-1

e. Residues at 6 t ha-1

+ 50% of label rate of chevalier 15 WG

f. Label rate of chevalier 15 WG (300 g/ha)

Chevalier 15 WG herbicide was sprayed on weeds of their

respective plots after 45 days from sowing of wheat, using hand sprayer a

Knapsack hand sprayer fitted with T-Jet nozzle at a pressure of 207 k Pa.

The experiment was conducted in split plot design with four replications

for each treatment. The herbicide rates were kept in the subplot while

sunflower residue rates were assigned as main plot. All plots received

equal irrigated water during the growing season of the crop.

2.3. Weed measurements:

2.3.1. Weed density (plant m‾2)

A quadrate measuring 0.5 × 0.5 m was randomly placed in

respective plots at 90 and 120 days after sowing to record weed density.

their average was calculated and converted to weed density per meter

square.

2.3.2. Weed biomass (g m‾2)

The weeds were counted at 120 days after sowing , cut from ground

surface, stored in polythene bags and then brought to laboratory for

recording their biomass. Total dry weight of weeds was determined after

oven-drying at 70˚C for 3 days until constant weight was achieved. The

weight was measured using an electric balance, averaged and calculated

on square meter basis.

2.4. Wheat crop measurements

2.4.1. Dry weight of plant through different stages of crop growth

(g/m2)

An area 20 cm was selected randomly from each plot at 27 ,44, 75,

and 103 day after sowing, cut from ground surface, stored in polythene

bags and then brought to laboratory for recording their dry biomass. The

dry biomass of plants was determined after oven-drying at 70˚C for 3

days until constant weight was achieved. The weight was measured using

an electrical balance, averaged and calculated on square meter basis.

2.4.2. Crop Growth Rate CGR (g/m2/day)

The following formulae proposed by Hunt (1982) was used to

calculate crop growth.

.1

12

12

TT

WW

ACGR

Where: W2 and W1 were the dry weight of plant and T2 and

T1 were the time of sampling.

2.4.3. Plant height

At harvesting, ten plants were selected randomly from each plot

and their height was measured from ground surface to the top of the plant

with the help of meter rod and the average height was calculated in cm.

2.4.4. Number of spikes/m2

An area of 0.5 × 0.5 m were selected at random in each plot to count

number of spikes at maturity and converted to number of spikes/m2

2.4.5. Number of grains per spike

Twenty spikes were selected randomly from each experimental

unit and threshed individually. The grains were counted and average

number of grains per spike was calculated.

2.4.6.1000-grain weight (g)

Two samples, each of 1000-grain, were taken from the produce of

each plot. These samples were weighed on an electric balance and

average 1000-grain weight was calculated.

2.4.7. Total wheat biomass (t ha1ـ)

The crop was harvested, tied into bundles and allowed to sundry for

a week in respective plant. Total wheat biomass of the sun dried samples

was recorded for each treatment. The total biomass yield per plot was

converted to tones per hectare (t haـ 1).

2.4.8. Grain yield (t haـ 1)

The harvested and sun dried crop was threshed manually. The grains

weight for each treatment was recorded in gram and later expressed in

tones per hectare (t haـ 1).

2.4.9. Biological yield

Biological yield was calculated by summation of straw and grain

weights.

2.4.10. Harvest index

Harvest index for each treatment was calculated by using the

following formula (Donald and Hamblin, 3454 ).

Harvest index = (Grain yield / Total biomass yield) ×100

2.5. Mycorrhizal studies

2.5.1. Spore extraction

Soil samples were collected from each plot, air dried and sieved

through a 2 mm openings sieve to remove large debris. A sub sample

(100 g) was taken from each sample and placed in a 500 ml beaker

containing 200 ml 0.08 M sodium hexametaphosphate solution to break

up clay clumps. The suspension was agitated for 5 minutes and left to

settle for 15 seconds (Smith and Dickson, 1997). The supernatant was

decanted through a nest of sieves with reducing mesh sizes from 500 μm,

250 μm, 125 μm to 45 μm. This step was repeated with water twice and

the debris from the 45 μm was discarded. The debris on the remaining

sieves, containing the AM spores was washed and placed in 40 ml

centrifuge tubes for purification. The spore suspension was centrifuged at

3000 rpm for 5 minutes, after which the supernatant was discarded. The

pellet was re-suspended in 60% sucrose solution and centrifuged for

another 5 minutes. The supernatant containing AM fungal spores was

decanted into a 45 μm sieve and washed with water to remove sucrose on

the spores (Smith and Dickson, 1997).

2.5.2. Isolation and identification of mycorrhiza spores

Some spores were mounted in small glass capsules containing water

and a drop of chloroform for identification. The identified according to

Schenck and Smith, year 1982.

2.5.3. Preparation of Mycorrhiza inoculums

Loamy soil was brought from field, sterilized in autoclave for 0.5 hr

period for two days and packed in 10 plastic pots of 1 kg capacity.

Spores of mycorrhiza Glomus mosseae were extracted by procedure

outlined by Smith and Dickson (1997). The extract was mixed with the

upper part of pot soil . Ten seeds of sorghum and 10 of millet were sown

separately and irrigated with appropriate amount of water. Three months

after planting, the above ground of plants were cut. The soil plus roots of

both plant species were taken, mixed thoroughly and used for inoculation

process (Matloob, 2012).

2.5.4. Spore counting

Based on previous field study, total phenolics was increased after

two weeks of residue decomposition and reach maximum accumulation

in December 15, 2012 of residues decomposition and declined drastically

thereafter. To test if the mycorrhizal population is correlated with the

phenolics profile during this period, spore counting was conducted by

taking soil samples from rhizosphere of wheat plants growing in plots

containing 6 t ha-1

and in plots without sunflower residues (Control) at 1,

14, 28 and 42 days after sowing (DAS).

Spore counting was also made at the end of wheat crop maturity to

determine the possible effect of test treatments on mycorrhizal population

and growth. Soil samples from rhizosphere of wheat plants growing in

plots of all treatments were taken and used for counting number of spores

using microscopic slide.

2.5.5. Mycorrhizal colonization rate (%)

Wheat plant roots were taken from the field at the end of crop

maturity for determining the colonization rate and colonization intensity.

Fresh roots were carefully washed and cut into 1-3 cm pieces. The pieces

were immersed with 1% KOH solution and incubated at 70°C for 20

minutes to remove the cytoplasm. The KOH solution was discarded and

the roots were rinsed well with distilled water. Roots were covered with a

freshly prepared alkaline H2O2 solution for 10 minutes. The bleaching

solution was discarded and the roots were rinsed with water. Roots were

acidified in a 0.1 M HCl solution overnight to ensure adequate binding of

stain to fungal structures. The HCl solution was discarded and roots were

covered with Lacto glycerol Trypan Blue (0.05%) stain and incubated for

45 minutes at 90°C. The stain was poured off and roots were covered

with lacto glycerol destain. Roots were allowed to destain overnight

before microscopic examination (Smith and Dickson, 1997). Finally,

roots were mounted on microscopic slides and using a compound

microscope for examined. The percentage root colonization was

calculated by the following equation using a modified Line Intersect

Method (Mc Gonigle et al., 1990) (Appendix 1,2,3,4).

% Colonization = (Total number of AM positive segments / Total number

of segment studied) × 100

Mycorrhizal intensity was calculated based on the following rate

index.

0 = the root fragment was not mycorrhizaled

1 = 1-25 of the root fragment was mycorrhizaled

2 = 26-50 of the root fragment was mycorrhizaled

3 = 51-75 of the root fragment was mycorrhizaled

4 = 76-100 of the root fragment was mycorrhizaled

Mycorrhizal intensity (MI) was calculated according to the

following equation:

MI = Total (number of fragments × their rate index) / number of observed

fragments × highest rate

2.6. Determination of total phenolics Folin-Denis was used for total phenol analysis (A.O.A.C., 1990) and

ferulic acid was used as standard since it is an allelopathic agent present

in sunflower plant (Haslam, 1988). Soil samples were taken from soil of

plots amended with 6 t ha-1

and 0 t ha-1

(control) at a depth of 30 cm at 1,

14, 28 and 42 days after sowing (DAS). The soils were mixed thoroughly

and allowed to dry at room temperature for 3 days. Samples of 250 g dry

soil were extracted separately in 250 ml of distilled water by shaking for

24 hrs at 200 rpm (Ben- Hammouda et al.,1995). Soil suspensions were

filtered through Whatman No. 2 filter paper under vacuum. Folin-Denis

(0.5 ml) and Na2CO3 (one ml) were added to one ml of soil water extract

and left to stand for 30 minutes. Absorbance was determined at 750 nm

on aspectrophotometer (Blum et al.,1991). The total phenolic content was

obtained by standard curve using different concentrations of ferulic acid

(Appendix 5,6,7).

2.7. Bioassay of soil amended with sunflower residues

Soil samples were taken from soil of plots amended with 6 t ha-1

and 0 t ha-1

(control) at a depth of 30 cm at 1, 14, 28 and 42 days after

sowing (DAS). The soils were mixed thoroughly and allowed to dry at

room temperature for 3 days. Samples of 200 g dry soil packed in plastic

pots of 250 g capacity. Ten seeds of Malva rotundifolia L. was sown in

each pots. The pots were arranged in randomized complete blocks in

three replications in plastic house at the beginning of December. The pots

were irrigated with appropriate amount of water whenever needed. Seed

germination was recorded 15 days after sowing, after which time, the

seedlings were thinned to 3 per pot and allowed to grow for additional

two weeks. The plants were pulled from the pots using running water.

Total dry weight of M. rotundifolia L was determined after oven-drying

the plants at 70˚C for 3 days. The weight was measured using an

electrical balance.

2.8. statistical analysis

The collected data were statistically analyzed using analysis

of variance (ANOVA) by GENSTAT computer software package.

Differences among treatment averages were compared using Least

Significant Difference (LSD) ≤ 0.05 probability level (Steel et al.,

1980).

Chapter Three

Results

CHAPTER THREE

RESULTS

3.1. Weed parameter

3.1.1. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on total weed density in wheat

field

Field observations showed that 70% of weeds species

grown in the wheat field were broad leaf viz. Beta vulgaris L.,

Ammi majus L., Malva rotundifolia L., Ducus carota L.,

Carthamus oxyacanthus M.B., Spergularia salina L., and the

remain was grass weeds, namely Avena fatua L., Lolium

temulentum L. and Phalaris minor L. (Table 2).

The result presented in table 3 revealed that soil

incorporation of sunflower residues at 3 t ha-1

significantly

reduced total weed density by 88 and 70% of control after 90 and

120 days after sowing (DAS), respectively. Similarly, weed

population was significantly increased by 89 and 78% over

control by the residue rate to 6 t ha-1

after 90 and 120 DAS,

respectively. The suppression of weed density was increased with

increasing rate of residues to 6 t ha-1

at 120 DAS only. However,

the inhibition of weed population by the residues rates was

significantly averted when the residues combined with the

herbicide. Foliar application of 50% of label rate of chevalier to

plots amended with sunflower residue at 3 and 6 t ha-1

significantly suppressed weed density more than the respective

residue rates when applied alone after 90 and 120 DAS.

Application of label rate of chevalier recorded the highest

reduction in weed density compared to all treatments.

Table 2. Weed species grown in the test wheat field.

Common name

Scientific name Family

Broad leaf - weeds

Common beet Beta vulgaris L.

Chenopodiaceae

Large bull wort Ammi majus L.

Umberlliferae

Mallow Malva rotundifolia L.

Malvaceae

Wild carrot Ducus carota L.

Umberlliferae

Wild safflower Carthamus oxyacanthus

Asteraceae

Salt sandsparry Spergularia salina L.

Caryophllaceae

Narrow- leaf weeds

Wild oat Avena fatua L.

Poaceae

Rye grass Lolium temulentum L.

Poaceae

Canary grass Phalaris minor L.

Poaceae

Table 3. Effect of different rates of chevalier 15 WG herbicide and sunflower residues cv. Asgrow on weeds population

grown in wheat .

Treatments

Population density

(Plants per m2)

at 90 DAS*

% of control

Population density

(Plants per m2)

at 120 DAS

of control %

Weedy check (Control) 480 ---- 184 ---

Residues at 3 t ha-1

60 12.5 55 29.9

Residues at 3 t ha-1

+ 50% of label

rate of chevalier15 WG 33 6.9 36

19.6

Residues at 6 t ha-1

53 11.0 40 21.7

Residues at 6 t ha-1

+ 50% of label

rate of chevalier15 WG 29 6.0 26 14.1

Chevalier15 WG (Label rate) 11 2.3 0 0

LSD ≤ 0.05 5.5 --- 10.9 ---

* DAS= day after sowing

3.1.2. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on dry weight biomass of

weeds in wheat

The results presented in table 4 revealed that average weed biomass

was significantly reduced by the residues of sunflower incorporated in

field soil. The reduction increased from 87% of control at 3 t ha-1

sunflower residue to 88% of control at 6 t ha-1

sunflower residue.

The interaction of herbicides and sunflower residues showed

significant effect on weed biomass. When chevalier applied at reduced

50% of label rate to plots amended with sunflower residues at 3 and 6 t

ha-1

scored weed biomass (94 and 96% of control respectively) more than

the residue rates when applied alone. However, chevalier application

(label dose) recorded maximum reduction (100%) in weed biomass.

3.2. Crop parameters

3.2.1. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on dry weight of wheat during

different growth stages

Result presented in figure 1 revealed the soil incorporation of

sunflower residue at 3 and 6 t ha-1

significantly inhibited dry

weight of wheat through the first two months after sowing and

the inhibition increased with increasing sunflower residues. At 75

DAS, no significant effect was appeared on dry weight of wheat

by application of sunflower residues alone. However, plots treated

with 50% of label rate of chevalier herbicide and amended with

sunflower residue at 3 t ha-1

recorded more dry weight (921.72

and 2023.2) than sole application of the 3 t ha-1

residue rate at 75

and 103 DAS, respectively. Similarly, plots treated with 50% of

label rate of chevalier and amended with sunflower residue at 6 t

ha-1

posed more dry weight (617.92 and 1884) than the 6 t ha-1

residue rate applied alone after 75 and 103 DAS, respectively.

Application of label rate of chevalier recorded maximum increase

in dry weight of wheat compared to all treatment at 75 and 103

DAS.

Table 4. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on dry weight biomass of

weeds grown in wheat.

Treatments dry weight biomass

(g per m2)

% of control

Weedy check (Control) 149.62 -----

Residues at 3 t ha-1

19.76 13.2

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG 9.26 6.2

Residues at 6 t ha-1

17.37 11.6

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG 6.46 4.3

Chevalier15 WG (Label rate) 0.00 -----

LSD ≤ 0.05 3.5 -----

Figure 1. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on dry weight of wheat.

T1. Control (uncultivated sunflower field), T2. Residues at 3 t ha-1

, T3. Residues at 3

t ha-1

+ 50% of label rate of chevalier WG, T4. Residues at 6 t ha-1, T5. Residues at 6 t

ha-1

+ 50% of label rate of chevalier15 WG, T6. Chevalier WG (Label rate).

0

500

1000

1500

2000

2500

27 44 75 103

Days after sowing

Dry

we

igh

t (g

/m2)

T1 T2 T3 T4 T5 T6

LSD≤ 0.05 2.43 8.93 77.5 87.7

3.2.2. Effect of different rates of chevalier 15 WG herbicide

and sunflower residues cv. Asgrow on crop growth rate

of wheat crop

The result presented in figure 2 revealed that soil

incorporation of sunflower residue at 3 and 6 t ha-1

showed

significant effect on crop growth rate of wheat during first 75

days after sown. Crop growth rate was decreased by 31 and 48%

of control by application of sunflower residue at 3 and 6 t ha-1

at

27 DAS. While the effect continue until 44 DAS, plots treated

with 50% of label rate of chevalier herbicide and amended with

sunflower residue at 3 and 6 t ha-1

more increase of crop growth

rate than the respective residue rate applied alone and control

treatments. Maximum crop growth rate was recorded by the

reduced rate of herbicide and sunflower residue rate at 6 t ha-1

after 75 DAS followed by a decrease in order by T6> T3> T2 >T1

respectively.

3.2.3. Grain yield (t ha-1

)

The result in table 5 revealed that the grain yield appeared to be

significantly affected by herbicide and sunflower residue treatments. The

grain yield was increased by 58 and 37% of the control when sunflower

residues were incorporated into the field soil at 3 and 6 t ha-1

,

respectively. However, plots treated with 50% of label rate of chevalier

herbicide and amended with sunflower residue at 3 t ha-1

recorded higher

yield than the respective residue rate applied alone and the label rate of

herbicide treatments. Similar trend of increase was observed with the

higher residue rate when combined with the reduced dose of herbicide.

Plots treated with 50% of label rate of chevalier herbicide and amended

with sunflower residue at 6 t ha-1

recorded higher yield than sole

application of residue rate at 6 t ha-1

.

The results revealed that sunflower residue at a rate of 6 t ha-1

applied alone or in combination with reduced rate of herbicide yield

grains significantly lower than the residue rate of 3 t ha-1

alone or with

reduced rate of herbicide.

Figure 2. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on crop growth rate of wheat.

T1. Control (un cultivated sunflower field), T2. Residues at 3 t ha-1

, T3.

Residues at 3 t ha-1

+ 50% of label rate of chevalier WG, T4. Residues at 6 t

ha-1, T5. Residues at 6 t ha

-1 + 50% of label rate of chevalier15 WG , T6.

Chevalier WG (Label rate).

0

5

10

15

20

25

30

35

40

45

50

27 44 75

Day after sowing

Cro

p g

row

th r

ate

(g

/m2/d

ay

)

T1 T2 T3 T4 T5 T6

LSD ≤ 0.05 0.71 2.63 4.14

Table 5. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on grain yield of wheat crop.

Treatments Grain yield

(t ha-1

)

% of control

Weedy check (Control) 3.8 ---

Residues at 3 t ha-1

6.0 57.93

Residues at 3 t ha-1

+ 50% of label

rate of chevalier 15 WG 6.7 76.33

Residues at 6 t ha-1

5.2 36.83

Residues at 6 t ha-1

+ 50% of label

rate of chevalier 15 WG 5.8 152.6

Chevalier 15 WG (Label rate) 6.4 68.43

LSD ≤ 0.05 0.3 ---

3.2.4. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on yield components of wheat

3.2.4.1. Effect on number of spikes per m2

All treatments significantly affected number of spikes

compared to the control (Table 6). Plots amended with sunflower

residues at 3 and 6 t ha-1

increased number of spikes by 43 and

37% over control, respectively. Plots treated with 50% of label

rate of chevalier herbicide and amended with sunflower residue at

3 t ha-1

recorded significantly more number of spikes than plots

treated with 3 t ha-1

residues alone. However, combination of 50%

of label rate of herbicide with sunflower residue at 6 t ha-1

did not

significantly increase the number of spikes over 6 t ha-1

residues

treatment alone. Maximum increase was recorded in plots treated

with label rate of chevalier herbicide.

3.2.4.2. Effect on grains per spike

The average number of grains per spike was significantly

increased by 16 and 23% over control by incorporation of

sunflower residues at 3 and 6 t ha-1

, respectively (Table 7 ).

Herbicide application at reduced (50%) dose to plots amended

with test sunflower residues scored decrease number of grains per

spike compared to this sunflower residues when applied alone and

control (without sunflower residue). Meanwhile, Reduced

herbicide (50 %) dose in combination with 3 t ha-1

sunflower

residue rate scored similar number of grains per spike as was

observed under sole application of the label dose.

3.2.4.3. Effect on 1000-grain weight (g)

All test treatments significantly affected 1000-grain

weight compared to the control (Table 8). Incorporation of

sunflower residues in the field soil at rates of 3 and 6 t ha-1

significantly reduced 1000-grain weight by 8 and 7 over control

respectively; however, this increment was further hastened to

become greater than the label rate of herbicide treatment when

reduced dose (50%) of chevalier was applied to plots amended

with sunflower residues at 3 and 6 t ha-1

.

Table 6. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on number of spikes of wheat.

Treatments Number of spikes per m2 % of control

Weedy check (Control) 368 ---

Residues at 3 t ha-1

526 142.9

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG 577 156.8

Residues at 6 t ha-1

504 137.0

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG 537 145.9

Chevalier15 WG (Label rate) 634 172.3

LSD ≤ 0.05 29.05 ---

Table 7. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on number of grains per spike of

wheat.

Treatments Number of grains per

spike

% of control

Weedy check (Control) 36.62 ---

Residues at 3 t ha-1

42.60 116.3

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG 32.06 87.5

Residues at 6 t ha-1

45.03 123.0

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG 32.96 90.0

Chevalier15 WG (Label rate) 30.82 84.2

LSD ≤ 0.05 2.90 ---

Table 8. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on weight of 1000 grains of

wheat.

Treatments Weight of 1000

grains (g)

% of control

Weedy check (Control) 33.72 ---

Residues at 3 t ha-1

36.46 108.1

Residues at 3 t ha-1

+ 50% of label

rate of chevalier15 WG 39.30 116.5

Residues at 6 t ha-1

36.06 106.9

Residues at 6 t ha-1

+ 50% of label

rate of chevalier15 WG 37.77 112.0

Chevalier15 WG (Label rate) 37.30 110.6

LSD ≤ 0.05 1.47 ---

3.2.5. Biological yield (t ha-1

)

The results in table 9 revealed that the biological yield was

significantly affected by herbicide and sunflower residues

treatments compared to control. The biological yield was

increased by 36 and 22% of the control when sunflower residues

were incorporated in to the field soil at 3 and 6 t ha-1

, respectively.

However, these increments were significantly (56% of control) or

appreciably (29% of control) improved when the reduced dose of

herbicide was applied to plots amended with sunflower residue at

3 and 6 t ha-1

, respectively. Apparently, the residue rate 6 t ha-1

alone or in combination with the reduced dose of chevalier

herbicide recorded biological yield lower than the respective

treatments of 3 t ha-1

and the label rate of herbicide.

3.2.5. Biomass (t ha-1

)

The results in table 10 revealed that the biomass was

significantly affected by herbicide and sunflower residues

treatments compared to control. The biomass was increased by 29

and 20% of the control when sunflower residues were

incorporated in to the field soil at 3 and 6 t ha-1

, respectively.

However, these increments were significantly improved when the

reduced dose of herbicide was applied to plots amended with

sunflower residue at 3 and 6 t ha-1

, respectively. Apparently, the

residue rate 6 t ha-1

alone or in combination with the reduced dose

of chevalier herbicide recorded biomass lower than the respective

treatments of 3 t ha-1

and the label rate of herbicide.

Table 9. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on biological yield of wheat crop.

Treatments Biological yield

(t ha-1

)

% of control

Weedy check (Control) 14.00 ---

Residues at 3 t ha-1

19.05 136.1

Residues at 3 t ha-1

+ 50% of

label rate of chevalier 15 WG 21.78 155.6

Residues at 6 t ha-1

17.03 21.63

Residues at 6 t ha-1

+ 50% of

label rate of chevalier 15 WG 18.03 128.8

Chevalier 15 WG (Label rate) 19.81 41.53

LSD ≤ 0.05 1.34 ---

Table 10. Effect of different rates of chevalier 15 WG herbicide

and sunflower residues cv. Asgrow on biomass of wheat.

Treatments Biomass (t ha-1

) % of control

Weedy check (Control) 10.14 -----

Residues at 3 t ha-1

13.04 128.6

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG 15.06 148.5

Residues at 6 t ha-1

12.13 119.6

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG 12.16 119.9

Chevalier15 WG (Label rate) 13.37 131.9

LSD ≤ 0.05 1.53 -----

3.2.7. Harvest index

All treatments enhanced the harvest index over the control

(Figure 3). Application of sunflower residue at 3 and 6 t ha-1

significantly increased harvest index by 14 and 12% over the

control. Maximum harvest index (32.32) was recorded by

treatment of residues at 6 t ha-1

+ 50% of label rate of chevalier15

WG, which is statistically at par with treatment of Label rate of

Chevalier 15 WG.

Figure 3. Effect of different rates of chevalier15 WG herbicide

and sunflower residues cv. Asgrow on Harvest index

of wheat.

T1. Control (un cultivated sunflower field), T2. Residues at 3 t ha-1

, T3.

Residues at 3 t ha-1

+ 50% of label rate of chevalier WG, T4. Residues

at 6 t ha-1

, T5. Residues at 6 t ha-1

+ 50% of label rate of chevalier15 WG

, T6. Chevalier WG (Label rate).

0

5

10

15

20

25

30

35

T1 T2 T3 T4 T5 T6 LSD ≤ 0.05

Treatments

He

rve

st

ind

ex

3.2.8. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on plant height of wheat

Plant height was significantly affected by the rates of

herbicide and sunflower residues and their interaction (Figure 4).

Application of sunflower residues at 3 and 6 t ha-1

significantly

reduced plant height by 39 and 6% of control respectively.

However, this reduction was further increased (4 and 8% of

control) when plots treated with 50% of label rate of chevalier

herbicide and amended with sunflower residues at 3 and 6 t ha-1

respectively. Maximum plant height (94.23 cm) was recorded by

control treatment and 3 t ha-1

treatments.

Figure 4. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on plant height of wheat.

T1. Control (un cultivated sunflower field), T2. Residues at 3 t ha-1

, T3. Residues

at 3 t ha-1

+ 50% of label rate of chevalier WG, T4. Residues at 6 t ha-1

, T5.

Residues at 6 t ha-1

+ 50% of label rate of chevalier15 WG , T6. Chevalier WG

(Label rate).

0

10

20

30

40

50

60

70

80

90

100

pla

nt

hei

gh

er (

cm)

T1 T2 T3 T4 T5 T6 LSD ≤

0.05

Treatments

3.3. Determination of Total phenolics in field soil

Total phenolics in field soil significantly increased after

incorporation of sunflower residues and reached their peak at 4

weeks of residues decomposition, then decreased significantly at 6

weeks and vanished at 6 weeks (Figure 5).

Figure 5. Total phenolics released in field soil amended with sunflower

residues at 6 t ha-1

during different decomposition periods.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1 14 28 42 L.S.D ≤ 0.05

Decomposition periods (days)

To

tal p

he

no

lic

s (

mg

/g d

ry

so

il)

Sunflower residues rate of 6 t.ha-¹ control (without sunflower residue) L.S.D ≤ 0.05

3.4. Weed bioassay

3.4.1. Seed germination of malva rotundifolia

Seed germination of malva rotundifolia was significantly

reduced after incorporation of sunflower residues in to the soil and

reached its maximum reduction at 4 weeks of residues

decomposition, then decreased significantly at 6 weeks (Figure 6).

Figure 6. Seed germination of Malva rotundifolia in field soil

amended with sunflower residues at 6 t ha-1

during

different decomposition periods.

0

0.2

0.4

0.6

0.8

1

1.2

1 14 28 42 L.S.D ≤ 0.05

Decomposition periods (days)

Seed

germ

ina

tio

n %

Sunflower residues rate of 6 t.ha-¹ control (without sunflower residue) L.S.D ≤ 0.05

3.4.2. Total dry weight of Malva rotundifolia

Total dry weight of malva rotundifolia in pots containing

field soil significantly reduced after incorporation of sunflower

residues and reached the maximum reduction at 4 weeks of

residues decomposition and gradually increased at the end of the

6th

week (Figure 7).

Figure 7. Total dry weight of Malva rotundifolia in field soil amended

with sunflower residues at 6 t ha-1

during different

decomposition periods.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

1 14 28 42 L.S.D ≤ 0.05

Decompsition periods (days)

Total

dry w

eig

ht

Sunflower residues rate of 6 t.ha-¹ control (without sunflower residue) L.S.D ≤ 0.05

3.5. Mycorrhizal studies

3.5.1. Isolation and identification of mycorrhiza from field soil of

wheat crop

Microscopic examination of the collected samples from

wheat field revealed that the dominant (90 % of the population)

species of mycorrhiza is Glomus mosseae. The species is

characterized by the following characters: spores are rarely filled

with hyphae, sporocarp containing 1-10 spores (sometimes),

diameter of subtending hyphae at widest part 18-50 µm, outer

surface of inner wall is not ornamented; thin, hyaline outer wall

may not be obvios. Spores are more than 100 µm in size,

subtending hyphae is generally funnel-shaped with cup-shaped

septum (Figure 8, 9).

Figure 8. spore of Glomus mosseae Figure 9. Sporocarp

X40 X4

0

hyphea

spore

3.5.2. Effect of different periods of decomposition of sunflower

residues in field soil before chevalier application on sporulation

Figure 10 showed the sporulation of Glomus mosseae in field

soil amended with sunflower residues at different periods of

decomposition and before the time of chevalier herbicide

application. The results revealed that incorporation of the residues

significantly increased spores number at 2, 4 and 6 weeks of

residue decomposition compared to control treatment (without

sunflower residue).

Figure 10. Sporulation of Glomus mosseae in field soil amended with

sunflower residues at 6 t ha-1

during different decomposition

periods.

0

50

100

150

200

250

300

1 14 28 42 L.S.D ≤ 0.05

Decomposition periods (days)

Sp

oru

lati

on

(sp

ore/1

00

dry s

oil

)

Sunflower residues rate of 6 t.ha-¹ control (without sunflower residue) L.S.D ≤ 0.05

3.5.3. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on sporulation at flowering

stage

The results presented in table 11 exhibited that sunflower residues

incorporated in field soil had a significant effect on number of spores.

Field soil amended with sunflower residues at 3 and 6 t ha-1

increased

number of spores by 16 and 23% over control. However, the number of

spores was decreased significantly when chevalier was applied at the

label dose. Chevalier application at reduced (50% of the label rate) rate

applied to plots amended with sunflower residue at 3 t ha-1

scored spore

number significantly lower than control treatment.

3.5.4. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on colonization rate of Glomus

mosseae

The results showed that colonization intensity was

significantly affected by herbicide and sunflower residues

application (Table 12). Sunflower residues incorporated into field

soil at rates of 3 and 6 t ha-1

significantly increased colonization

rate by 94 and 113% over control by 94 and 113 over the label

rate of herbicide, respectively. However, combination of reduced

dose of herbicide and the test rates of sunflower residues

significantly lowered colonization rate compared to sole

application of sunflower residue rates. Application of chevalier

did not affect rate and intensity of colonization significantly in

comparison to the control.

Table 11. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on number of spores of

Glomus mosseae associated with wheat roots.

Treatments Number of spores per

100 g dry soil

% of control

Weedy check (Control) 363.5 ---

Residues at 3 t ha-1

420.5 115.7

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG

299.0 82.3

Residues at 6 t ha-1

448.8 123.5

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG

341.2 93.9

Chevalier15 WG (Label rate) 241.5 66.4

LSD ≤ 0.05 27.9 ---

Table 12. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on colonization rate of Glomus

mosseae associated with wheat roots.

Treatments Colonization rate (%) % of control

Weedy check (Control) 40.00 ---

Residues at 3 t ha-1

77.50 193.8

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG

45.00 112.5

Residues at 6 t ha-1

85.00 212.5

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG

50.00 125.0

Chevalier15 WG (Label rate) 40.00 100.0

LSD ≤ 0.05 7.41 ---

3.5.5. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on colonization intensity of

Glomus mosseae

Sunflower residues significantly affected colonization intensity of

Glomus mosseae while application of herbicide did not significantly affect

colonization intensity (Table 13). Incorporation of sunflower residues

significantly stimulated colonization intensity by 99 and 107% over control

and by 136 and 145% over the label rate of herbicide. However,

combination of sunflower residues and reduced herbicide provide

colonization intensity statistically lower than sole application of respective

residue rates and similar to control and label rate of herbicide.

Table 13. Effect of different rates of chevalier 15 WG herbicide and

sunflower residues cv. Asgrow on colonization intensity

Glomus mosseae associated with wheat roots.

Treatments Colonization

Intensity (%)

% of control

Weedy check (Control) 40.00 ---

Residues at 3 t ha-1

79.50 198.8

Residues at 3 t ha-1

+ 50% of

label rate of chevalier15 WG

37.50 93.8

Residues at 6 t ha-1

82.75 206.9

Residues at 6 t ha-1

+ 50% of

label rate of chevalier15 WG

37.25 93.1

Chevalier15 WG (Label rate) 33.75 84.4

LSD ≤ 0.05 6.97 ---

Chapter Four

Discussion

CHAPTER FOUR

Discussion Allelopathy has been reported to offer a significant role in weed

control (Sodaeizadeh and Hosseini, 2012). Several non herbicidal weed

control strategies in which Allelopathy is involved has been explored such

as rotational crop, cover crop, smother crop, intercropping, crop mixtures,

water extract and use of allelopathic crop residues as mulch or incorporated

in field soil (Mohammadi, 2013) . Of the all of these strategies, use of

allelopathic plant residues is the most successful, effective and readily

available (Kelton et al., 2012). Nevertheless, the efficacy of crop residues

is not comparing with the efficacy of the herbicides. Hence the present

study was focused to test if we can improve the efficacy of sunflower

residues by integrated it with the lower doses of herbicide.

In present study, the inhibitory effect of sunflower residues

incorporated into the field soil suggests that the residues contain phytotoxic

materials released into the rhizosphere by dissolving in irrigation water

and/or by the action of soil microorganisms and affect the receiver plants.

Several investigators indicated that the residues of allelopathic plants are

the main source of allelopathic compounds in natural and agricultural

ecosystems (Singh et al., 2003; Batish et al., 2001; Alsaadawi and Dayan,

2009). The increase in phytotoxicity against weed density and biomass due

to increase in rate of residues in soil may be attributed to the increase of the

concentration of allelopathic compounds released from the residues into the

field soil. Similar results were reported in sunflower and other plant species

by several researchers (Alsaadawi et al., 1986b; Alsaadawi et al., 1998;

Sarbout, 2010). However, this trend of inhibition was not taken place with

wheat crop. The lower dose (3 t ha-1

) was found to have more stimulatory

effect on growth and yield than the higher dose (6 t ha-1

). This suggests that

the response of plant to phytotoxins is a concentration and species

dependent. The differential response of plant species to phytotoxins was

reported by different investigators. Weston (1996) mentioned that the large

seed plants are more tolerant to phytotoxins than the small seeds plants

such as weed. An et al, (1996) reported that allelopathic residues added to

the soil should be regulated to avoid the negative impact of the higher

amount of allelopathic residues by increasing seeds rate and/or remove

some of the allelopathic residues.

The presence and release of phytotoxins from the residues

incorporated into soil is further confirmed by the experiment of phenolics

determination in soil. Phenolics appeared to be released after incorporation

in soil, reached maximum beak at 4th

week of decomposition and then

declined until vanished at the end of 6th week (Figure 5). No attempt was

made to isolate and identify the phenolic acids in the decomposed

sunflower residues in soil; however, several investigators (Al-Temimi,

2010 ; Sarbout, 2010) were able to isolate and identify phenolic acids,

namely Chlorogenic acid, isolchlogenic acid, caffeic acid, gallic acid,

syrinigic acid, hydroxy benzoic acid, p- coumaric acid, ferullic acid,

vanillic acid and Catechol from the soil containing sunflower residues

and they reached their maximum beak at 4th week and vanished at 2

nd

month from incorporation of residues in to the field soil. These phytotoxins

are reported to have inhibitory effects on several metabolic processes such

as inhibition of chlorophyll biosynthesis (Alsaadawi et al., 1986a ; Weir et

al., 2004), ions uptake (Olmsted and Rice, 1970; Alsaadawi et al., 1986a;

Lehman and Blum, 1999), photosynthesis (Hejl et al., 1993), inhibition of

activity of plasma H+-ATPase which leads to decreased ions and water

absorption by guard cells of leaves and causing close of stomata (Hejl and

Koster, 2004), inhibition of photosystem II and thus decreases the

production of ATP and NADPH2 required for CO2 fixation in dark reaction

(Barkosky et al., 2000) , inhibition of oxidation phosphorylation (Koeppe

and Miller, 1974), inhibition of activity of several enzymes involved in

essential metabolic processes (Politycka and Gmerek, 2008), interfering

with hormones metabolism in plant. Inhibition of stomata opening (Rai et

al., 2003). Also phenolic acids are reported to reduce the number of

mitochondria and disrupt the membranes surrounding nuclei, mitochondria

and dictyosomes (Lorber and Muller, 1976).

Field observations indicated that low percentage of weeds emerged

at the beginning of sowing time and continued for about 6 weeks after

emergence then started to increase rapidly. Chemical analysis revealed that

phenolic acids were highly increased until reached maximum at 4 weeks

from sowing time then started to decline until vanished at 6 weeks from

sowing time. Thus, it appeared that the increase in concentration of total

phenolic acids in soil was parallel with high suppressive activity of weeds

in the field and vice versa. These results suggested that phenolics are the

main cause of the suppressive activity of weeds. Another evidence of

phenolic responsibility for the weed inhibition is the results of weed

bioassay experiment. The inhibition of seed germination and seedling

growth of Malva rotundifolia weed was highly correlated with the

increase concentration of total phenolics in field soil (r = 0.71 and 0.94

between phenolics concentration , seed germination and seedling growth,

respectively). At the end of 2nd

month from sowing, weeds started to

emerge and grow rapidly; however at that time, the crop plants became

large and highly competitive to weeds. These observations were also

reported when the residues of sorghum were added in broad bean field AL-

bedairy, 2011).

The potential inhibition of incorporated sunflower residues against

weeds population suggested that sunflower residues provide a significant

inhibitory effect. Maximum inhibition (78%) was achieved by incorporated

sunflower residues at 6 t ha-1

and this inhibition did not match with the

efficacy of the test herbicide. However, when this amount of residues

integrated with reduced dose of chevalier herbicide, a great reduction of

weed population (86%) and weed biomass (96%) was achieved and this

reduction can be comparable with efficacy of standard herbicides. This

result confirmed the previous hypothesis proposed by Bhowmik and

Inderjit (2003) that herbicides applied in combination with allelopathic

conditions could have a complementary interaction, and may help to

minimize herbicide usage for weed management in field crops. It seems

that a reduced level of herbicide may be feasible for providing satisfactory

weed control when it works simultaneously with allelopathic conditions.

The combination of allelopathy and herbicides has been suggested by

several scientists for a long time and very interesting results have been

obtained (Cheema et al., 2003a; Cheema et al., 2003c ; Iqbal and Cheema,

2008). However most of the work was done on water extract and no

experiments were conducted on the use of residues of allelopathic crops

including sunflower with herbicides. Our method is easy to conduct in the

field and the added residues would improve the soil physical properties and

nutritional status in addition to allelopathic potential against weeds.

The improvement in grains and biological yields by sunflower

residues alone or in combination with reduced dose of chevalier herbicide

seems an outcome of reduced weed-crop competition for any of the growth

factors which might have contributed to higher yields. It appeared that

weed suppression was directly translocated into yield so that significant

yield improvement over weedy check was realized by all treatments and

their various combinations. Improvement in crop yield and related

components by integrating allelopathy with reduced herbicide dose is in

line with the previous findings of Alsaadawi et al. 2011a and Khaliq et al.

(2012a,2012b).

Analysis of yield components indicated that the increase in number

of spikes per plant was the only one responsible for the increase in yield of

wheat crop. Similar result was recorded when the effect of sorghum residue

was tested alone or in combination with reduced dose of chevalier on wheat

yield and yield components (AL-bedairy, 2011).

The increase in the yield of wheat due to sunflower residue and

herbicide treatments is parallel to significant reduction in weeds population

and biomass. The higher residue concentration alone or in combination

with reduced dose of herbicide increased yield of wheat over control but

inhibited the yield when compared to the label rate of herbicide. This

suggests that the inhibition was due to the phytotoxicity of the higher

concentration of sunflower residues. The lowest level of residue (3 t ha-1

)

apparently was sufficient, when combined with reduced dose of chevalier,

to reduce weeds population and biomass (80 and 94%) over control and

provided yield greater than the label rate of the herbicide. Similar trend of

effect was reported when residues of sorghum and sunflower were applied

to different types of crops treated with lower rates of pre and post

emergence herbicides (Alsaadawi et al, 2011a; Alsaadawi and AI-Temimi,

2011; AL-bedairy, 2011).

The increase of harvest index due to residues application alone or in

combination with the reduced rate of herbicide suggests that much of

nutrients provided from weed suppression is translocated towards the

production of grains rather than to vegetative structures of wheat.

The present study revealed that the combined effect of crop residues

and reduced chevalier herbicide not only directly affect wheat crop but also

indirectly through their positive impact on sporulation, colonization and

hyphal growth of Glomus mosseae. In our study, the better sporulation was

observed during the period of phytotoxins relase from sunflower residues

in to soil (during the first 6 weeks from sowing). This suggests that the

phenolics pose stimulatory or at least did not interfere with the growth of

Glomus mosseae fungi. Reports on the effect of phenolic acids on AM

fungi are controversial. Siqueira et al. (1992) indicated that

allelochemicals specially phenolics stimulated mycorrhizal colonization,

while others found that mycorrhizal colonization was suppressed by

phenolic acids released from allelopathic plants (Javaid, 2008; Riaz et al.,

2007; Wacker et al., 1990). The inhibition or stimulation of AM spore

germination and hyphal growth and branching was mainly depended on

concentration and type of allelochemicals present in soil rhizosphere

(Batish et al., 2007).

The inhibition of AM sporulation and colonization intensity by the

label dose of chevalier is coincided with general trends of the effect of most

herbicides on mycorrhiza (Abd-Alla et al., 2000). However, reduced dose

of chevalier in combination with higher rate of sunflower residues scored

sporulation and colonization intensity similar to that of control treatment. It

is possible that the residues may mitigate the effect of chevalier herbicide

when applied in combination.

The results of this study led to the conclusion that the sunflower

residues amended in field soil provided a good medium for growing

Glomus mosseae fungi and the allelochemicals released from the residues

did not interfere with the test growth parameters of Glomus mosseae.

Conclusions

and

Recommendations

Conclusions and Recommendations

Conclusions

1. Sunflower residue showed allelopathic inhibition on weeds grown

wheat field. However the efficacy of the residue is not comparable

with the herbicide.

2. Combination of sunflower residues and reduced rate (50% of the

labeled rate) of herbicides appeared to be more effective in

controlling weeds population and growth than sole application of

residues.

3. Integration of sunflower residues at 3 t ha-1

with reduced rate of

herbicide provided grain and biomass yields of wheat similar to

that achieved by labeled rate of herbicide.

4. Phenolic compounds in sunflower residues appeared to be released

in higher amount into the soil after two weeks of decomposition

and continued until 6 weeks then vanished. Weed suppression was

coincided with the higher concentration of phenolics in soil.

5. Sunflower residues amended in field soil was found to provide a

good medium for growing Glomus mosseae fungus and the

allelochemicals released from the residues did not interfere with

the test growth parameters of this fungus.

Recommendations

According to the results of this study, the following points are

recommended:

1. The allelopathic phenomenon can be integrated with lower rate of

herbicide as a useful agricultural practice for weed management in

order to reduce dependence on herbicides and achieve

agroecosystems sustainability.

2. Further investigations into the allelopathic potential of other crop

residues along with different herbicides under varying

environmental conditions need to be conducted to provide data

base on utilization of this practice in weed and crop management.

3. Redesigning of crop rotations based on allelopathic phenomenon

needs to be considered to achieve sustainability and reduce the

pesticide input in agroecosystems and thereby reducing the

environmental pollution.

4. The possible effect of this practice on beneficial soil microflora

other than mycorrhiza such as nitrogen fixing and nitrifying

bacteria needs to be investigated to obtain a comprehensive picture

on the importance of this practice in agricultural production.

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Appendices

Appendices

Appendix 1.

Preparation of Alkaline Peroxide H2O2

3 ml NH4OH (Ammonia) + 30 ml 10% H2O2 + 567 ml distilled

water

Appendix 2.

Preparation of 0.1 M HCl (32% MW 36.46)

22.79 ml HCl

2 L Distilled water

Appendix 3.

Preparation of Lacto glycerol Trypan blue stain

520 ml lactic acid

480 ml Glycerol

640 ml distilled water

Mix the above compounds in a ratio of 13:12:16, respectively.

Then add 0.82 g Trypan blue to the mixture.

Appendix 4.

Preparation of Lacto glycerol Destain

520 ml lactic acid

480 ml Glycerol

640 ml distilled water

Mix the above compounds in a ratio 13:12:16, respectively.

Appendix 5. preparation of Folin-Denis Reagent

Amixture of 10g Na2WO4, 2 g phosphomolybdic acid, and 5 ml H3PO4 in

75 ml distilled water was refluxed for 2 h, cooled, and diluted to 100 ml

with distilled water.

Appendix 6. preparation of Sodium carbonate-saturated

anhydrous

Na2CO3 (4 g) was added to 10 ml distilled water and dissolved for 1 h at

70-80˚C, cooled, overnight, and filtered through glass wool.

Appendix 7. Ferulic acid standard solution

Ferulic acid (10 mg) was dissolved in 100 ml distilled water.

Aliquots of 0, 0.2, 0.4, 0.6, 0.8, and 1 ml of the standard ferulic

acid solution were dispensed into tubes containing 0.5 ml Folin-

Denis reagent and 1 ml saturated Na2CO3 solution. The standareds

were diluted to 10 ml with distilled weter and quickly shaken. A

bsorbance was determined after 30 min at 750 nm (Blum et

al.,1991) on a spectrophotometer (Pharmacia Ultra

spectrophotometer III).

Appendix 8. Effect of different rates of chevalier 15 WG herbicide

and sunflower residues cv. Asgrow on dry weight of wheat.

T1. Control (uncultivated sunflower field), T2. Residues at 3 t ha-1

, T3. Residues at 3

t ha-1

+ 50% of label rate of chevalier WG, T4. Residues at 6 t ha-1, T5. Residues at 6 t

ha-1

+ 50% of label rate of chevalier15 WG, T6. Chevalier WG (Label rate).

Appendix 9. Local, common and scientific names of plant species

appeared in the thesis

0

500

1000

1500

2000

2500

Days after sowing

Dry

weig

ht

(g/m

2)

T1 T2 T3 T4 T5 T6

T1 23.92 196.88 644.2 1311.6

T2 16.84 136.4 721.8 1654

T3 16.84 136.4 921.72 2023.2

T4 14.84 104.08 796.04 1457.2

T5 14.84 104.08 617.92 1884

T6 23.92 196.88 1033.56 2240.4

27 44 75 103

Local Arabic

name

Common name Scientific name

Acacia bark السنط النيلي

Acacia nilotica L.

.Alfalfa Medicago sativa L جت

Annual ryegrass حنيطة

Lolium rigidum L.

.Barley Hordeum vulgare L شعير

Barnyard grass دنان

Echinochloa crus-galli L.

Beet root wild سليجة

Beta vulgaris L.

Blady grass الحلفة

Imperata cylindrical L.

.Blond Plantago Plantago ovate Forssk لسان الحمل

.Broad bean Vicia faba L الباقالء

Broad leaved دنان

platran

Plantogo major L.

.Canola Brassica napus L سلجم

.Canary grass Phalaris minor Retz ابو دميم

.Celery cabbage Brassica campestris L سلجم صيني

.Cheese weed Malva pariflora L خباز

Clover البرسيم

Trifolium repens L.

.Cotton Gossypium hirsutum L القطن

.Belmude grass Cynodon dartylonl L الثيل المصري

.Darnel ryegrass Lolium temulentum L رويطة

Eucalyptus Eucalyptus camaldulensis يوكالبتوس

Dehnh.

.Flat sedge Carex spicata L البردي المفلطح

.Horse purslane Trianthema potrtulacastrum L خف الحصان

Johnson grass سفرندا

Sorghum halepense L.

Jungle rice دهنان

Echinochloa colona L.

Lamb's quarters رغيلة

Chenopodium album L.

Lentil Lens culinaris Medikus العدس

-Lesser swine الرشاد البري

cress

Coronopus didymus L.

الصفراءالذرة Maize Zea mays L.

Hairy-node bear زمزوم

grass

Dichanthium annulatum

Forssk.

Mulberry Morus Moraceae توت االبيض

Morus alba L.

.Mung bean Vigna radiate L الماش

Neem النيم

Azadirachta indica A.Juss

.Olive mill Olea europaea L زيتون

Pearl millet دخن

Pennisetum glaucum L.

.pigweed Portulaca oleracea L بربين بري

purple nutsedge سعد

Cyperus rotundus L.

.Common reed Phragmites australis L قصب البري

.rye Secale cereal L شيلم

red-root عرف الديك

amaranth

Amaranthus retroflexus L.

Rice الرز

Oryza sativa L.

.Safflower Carthamus tinctorius L العصفر

sorghum Sorghum bicolor L. (Moench) الذرة البيضاء

Soybean فول الصويا

Glycine max L.

Sunflower زهرة الشمس

Helianthus annuus L.

toothed dock ضرس العجوز

Rumex dentatus L.

.White top Weed Parthenium hysterophorus L االقحوان

.wheat Triticum aestivum L الحنطة

.wild oat Avena fatua L شوفان البري

الخالصة

والمختبريذذة الختبذذار الجالذذد االليلوبذذااي لمخلفذذات مجموعذذة مذذن التجذذارل الحقليذذةنفذذذت

فذي ماافحذة اغدغذال وحاصذل زهرة الشذمس بمفردهذا او مذر جرعذة منخفنذة مذن مبيذد الشذيفالير

الموسذم قليذة فذي الحتجربذة . فقذد نفذذت النمو الماياورايزا المتعايشذة مذر جذذور الحنطذة والحنطة

، اذ كليذة العلذوم، جامعذة بدذداد ،م الحيذاة في حقل تجارل قسم علو 8336-8338لعام الزراعي ل

طذذن هذذـ 8و 6 المضذذافة بمعذذدل Asgrowمخلفذذات زهذذرة الشذذمس صذذنف سذذتعملتا-3

بصذذورة

غم. هـ 373) مر نصف الاميةاو منفردة -3

( الموصى بالا من مبيد الشيفالير في ماافحة اغدغال

ومعاملذة مبيذد وحاصل الحنطذة. كمذا تضذمنت الدراسذة معاملذة مقارنذة بذدون ماافحذة ) مدغلذة(

ةأربعذوب RCBDتصذميم القطاعذات العشذوا ية الااملذة سذتعملللمقارنذة. ابالجرعة الموصى بالا

وحذذدد المحتذذوك الالذذي للفينذذوالت فذذي تربذذة الحقذذل المخلوطذذة بمخلفذذات زهذذرة الشذذمس .ماذذررات

هذذـطذذن 8بتركيذذز -3

المذذاياورايزا كمذذا تذذم عذذزل وتشذذخي مختلفذذة مذذن الزراعذذة. مذذدد خذذالل

و وحسذال عذدد السذبورات خذالل المراحذل اغولذى مذن نمذو الحنطذة المتعايشة مر جذور الحنطذة

يذد نسذبة ااصذابة وشذدتالا فذي مرحلذة تزهيذر نبذات الحنطذة فذي وعنذد مرحلذة التزهيذر. وتذم تحد

الحقل.

هطذذن 6تربذذة الحقذذل بمعذذدل ضذذافة الذذى مخلفذذات زهذذرة الشذذمس الم أنأظالذذرت النتذذا

يوما من الزراعة علذى 383و 43% عن المقارنة بعد 45% و 22اختزلت كثافة اغدغال بنسبة

ه طن 8وازداد هذا االختزال عند زيادة المخلفات المخلوطة إلى تابرالت-3

% 52و 24ليصل إلى

االختذزال ازداد بشذال كبيذر أال أن . تذابريوما مذن الزراعذة علذى الت 383و 43عن المقارنة بعد

إضافة نصذف الجرعذة وادت .نصف كمية مبيد الشيفالير مر مخلفات زهرة الشمس عملتاست عند

هطن 6مر مخلفات زهرة الشمس بتركيز من المبيد-3

مذن مذا حققتذ لألدغذال اعلذي اختذزالإلذى

ها.مفردب النسبة نفسالا من المخلفات إضافة معاملة

علذذى قذذد انعاذذس تذذاايرب ايجابيذذاالنتذذا إن االنخفذذا فذذي كثافذذة اغدغذذال لقذذد أظالذذرت

بينت النتا إن إضافة نصف الجرعة من المبيد مر مخلفذات زهذرة الشذمس بتركيذز فقد الحاصل.

هطن 6-3

لحبول بالسنبلة ودليذل للسنابل وعدد لحبول وعدد وحاصال لل ابيولوجي حاصالاعطت

من مبيد الشيفالير. الموصى بالامعاملة الجرعة مشاب لما اعطت لحصاد ل

يومذذا 39بعذذد الالذذي للفينذذوالت قذذد ازداد المحتذذوك وأظالذذرت نتذذا التحليذذل الايميذذا ي إن

أسابير مذن 8بعد ىهبط إلى إن تالش بعدهايوما من التحلل 82صل إلى اعلي مستوك ل بعد وو

محتذوك الالذي للفينذوالت فذي المذر بصورة معنويذة عاليذة تثبيط دغل الخباز وقد ارتبط التحلل.

فينوالت.للباز كان نتيجة الفعالية العالية لخاتثبيط دغل ان يشير إلى، التربة وهذا

رات في تربة الحقل المضاف إلي مخلفات زهرة وسبما نتا دراسة الماياورايزا، إن عدد االأ

أسذذابير مذذن تحلذذل مخلفذذات زهذذرة الشذذمس مقارنذذة بمعاملذذة 8 و 9 و 8 الشذذمس ازداد معنويذذا عنذذد

إما عند إضافة نصف الجرعة من المبيد مر مخلفات زهذرة المقارنة )بدون مخلفات زهرة الشمس(.

هطن 6الشمس بتركيز -3

فقد انخفض معنويا عدد السبورات أكثر من معاملة المقارنذة، إال إنذ عنذد

هطن 8إضافة نصف الجرعة من المبيد مر مخلفات زهرة الشمس بتركيز -3

عذدد السذبورات ازداد

6. إما عند إضافة مخلفات زهرة الشمس إلذى تربذة بتركيذز ارنةلتصل لما هو علي في المعاملة المق

هطن -3

وقد سجلت ألواح % عن المقارنة.44 و 49 الماياورايزا بنسبةبزادت نسبة وشدة ااصابة

هطذن 8و 6فيالا المخلفات إلى تربة الحقذل بنسذبة تالمعاملة التي أضيف-3

مذر نصذف الجرعذة مذن

ااصابة مقارنة بالسيطرة.المبيد زيادة معنوية في نسبة

جمهورية العراق

وزارة التعليم العالي والبحث العلمي

جامعة بغداد / كلية العلوم

قسم علوم الحياة

تأثير التكامل بين مخلفات زهرة الشمس و مبيد الشيفالير في

المايكورايزا ونمو مكافحة أدغال محصول الحنطة

جامعة بغداد -قسم علوم الحياة –كلية العلوم مجلس مقدمة إلى اطروحة

نباتفسلجة ال/علوم الحياة الدكتوراهوهي جزء من متطلبات نيل درجة

من قبل

ياء نصيف مسلم العكيلسر

6002 المستنصرية جامعةال/ كلية العلوم / بكلوريوس علوم الحياة

6009 الجامعة المستنصرية/ كلية العلوم / نباتماجستير

بإشراف

د. إبراهيم شعبان السعداوي . أ

هادي مهدي عبود د.

م 4153 هـ 5341