Egypt. J. Plant Breed. 19(1):55 – 70 (2014)

GENETIC ANALYSIS TO FIND SUITABLE PARENTS

FOR DEVELOPMENT OF CHERRY TOMATO HYBRIDS

UNDER GREEN HOUSE CONDITIONS A.M.A. Mahmoud

1 and A.A.S.A. El-Eslamboly

2

1Vegetable Crops Department, Faculty of Agriculture, Cairo University,

2Horticulture Research Institute, Agriculture Research center, Cairo, Egypt.

ABSTRACT Cherry tomato has the potential for improvement through heterosis breeding

which can further be utilized for development of desirable recombinants. A 7×7, half-

diallel mating design was used to determine heterosis over better parent, potence ratio,

combining ability and gene action for nine characters in cherry tomato. Preponderance

of additive gene action was evident for control of all characters studied except fruit

firmness and fruit ascorbic acid content for which both additive and non-additive gene

actions were evident. Generally, no particular cultivar or hybrid can be used to evaluate

all studied traits with equal efficiency. However, amongst the parental lines,

Solanumlycopersicum var. cerasiforme LYC 196/81 cv. Bubjekosoko (P1), PI 647522 cv.

Cal Red Cherry (P3) and PI 639207 cv. Black Cherry (P7) were the best general

combiners for fruit yield along with good quality traits and thus could be used in tomato

hybridization programs. Also, parent Solanum sp. PI 260402 cv. M-10 (P5) exhibited

highly significant general combining ability (GCA) effect in desired direction for fruit

contents of TSS, titratable acidity, ascorbic acid content, and lycopene. Some crosses

showing high significant specific combining ability (SCA) effects for fruit yield involved

parents showing high GCA for yield. The cross P1 × P7 exhibited highest significant

positive values of SCA of yield along with quality traits and this result incompatible with

those obtained in a performance evaluation trail of the produced hybrids with their

parents. The cross P6 (Solanum sp. PI 126915 cv. 125) × P7 exploited the best

combination for better quality traits.The general performances of the F1 hybrids reflected

the presence of various degrees of dominance effects; i.e., partial to overdominance for

the evaluated characters. Some produced F1 hybrids had significantly heterobeltiosisin

desired direction for the evaluated traits. Keywords: Cherry tomato, Solanumlycopersicum var. cerasiforme, Heterobeltiosis,

Dominance, Gene action, Combining ability.

INTRODUCTION

Cherry tomato,Solanumlycopersicum var. cerasiforme (Alef.)Voss,

is a botanical variety of the cultivated tomato and it is thought to be the

originator of all cultivated tomato types.Cherry tomato is grown for its

edible fruits, which are generally round, red when ripe, small (less than 30g)

and longer than 1.5 cm, but less than 3 cm in diameter (Kalloo 1991

andRancet al 2008).Cherry tomatoes are largely used for fresh consumption

and their commercial importance is continuously increasing because of their

high nutritional value, antioxidant properties and good taste (Kavthaet al

2014,Premaet al 2011and Renukaet al 2014).

Cherry tomato varieties are generally characterized by higher dry

matter and soluble solids levels than normal-sized fresh market cultivars;

these differences are due to the higher content of sugars (fructose and

glucose) and organic acids (citric and malic), which, in turn, are major

56

factors in determining the greater sweetness, sourness, and overall flavor

intensity of most cherry varieties (Causseet al 2003 andRenukaet al

2014).Cherry tomato is a rich source of antioxidants (mainly lycopene and

β-carotene), vitamin C, pro-vitamin A carotenoids, and minerals like Ca, P

and Fe in diet (Garcýa-Closaset al 2004,Lenucciet al 2006 andKavithaet al

2014), which are protective against infectious and degenerative diseases,

such ascardiovascular diseases (Marchioliet al 2001) or certain cancers

(Byers and Guerrero1995). For this reason, there is an emphasis on breeding

new tomato cultivars with nutraceutical value, but there has been less work

done with respect to quality improvement in cherry tomatoes. There has

been no breeding program targeted towards nutritive values in Egypt.

Many tomato breeding programs are directed toward the

development of superior Fl hybrids. Hybrids are preferred over pure line

varieties in tomato on account of their maturity earliness, more uniformity,

disease resistanceand superiority of marketable fruit yield and fruit quality

(Shankaraet al 2005). Thus, the cultivation of hybrid varieties is economical

and remunerative, and, therefore, the greater part of tomato crop is occupied

by hybrid varieties, especially in the greenhouse. Hybrid plants combine the

characters of the parent plants. Previous studies have suggested that

increasing genetic distances (variability) between parents, increases

heterosis, especially, heterobeltiosis (Melchinger 1999). The term heterosis

refers to the phenomenon in which the F1 population obtained by crossing

two genetically dissimilar individuals show increase or decrease in vigour

over the better parent (heterobeltiosis), over the average overall parents

(mid-parents heterosis), or over the best standard variety (standard

heterosis). Heterosis in desirable direction (hybrid vigour) is the ultimate

aim of breeders. Hence, there is great significance in the improvement of

methods for heterosis breeding and hybrid seed production.

Heterosis in tomato was first observed by Hedrick and Booth (1907)

for higher yield and more number of fruits per plant. Stoner and Thompson

(1966) reported that all crosses of small × small fruited strains and some

small × large fruited strains of tomato showed heterosis in the F1 with the

mean exceeding the top parent. Further genetic analysis indicated that

epistasis or non-allelic interactions were primarily responsible for heterosis.

Heterosis manifestation in tomato is in the form of greater vigour, faster

growth and development, earliness in maturity, increased productivity,

higher levels of resistance to biotic and abiotic stresses (Yordanov 1983).

Since then a number of workers have reported heterosis in tomato

(Metwallyet al 2003, Shalaby 2008, 2012 and 2013, Singh and Asati 2011,

and Solieman et al 2013).Khereba et al (2011) found a positive standard

heterosis of yield components and quality traits among 55 cherry tomato

hybrids produced and evaluated with standard hybrid cv. Sweet Million.

57

In any crop improvement program, the choice of the parents for

hybridization is one of the critical and the most difficult tasks for the

breeder. The fitness of cultivars and lines for use as partners in hybrid

combinations is determined not only by their economically valuable

characters but also by their ability to produce high heterosis effect in F1

crosses. This ability, called "combining ability", plays a great role in the

success of heterosis breeding. Therefore, test crosses for general and

specific combining ability must be primarilyachieved. GCA reveals the

existence of additive gene effects, while SCA reveals non-additive gene

effects and additive × dominance and dominance × dominance interactions.

Information about GCA effects are beneficial in choosing best combiner

parents and SCA effects information reveal best cross combinations for

further judgment. Judicious application of information relevant to standard

heterosis and SCA are fruitful for selecting best hybrids for desired traits

(Moore and Currence 1950).

The present study was carried out to identify the best combiner

parents of cherry tomato accessions and best cross combinations between

themfor developing promising hybrids for yield and quality traitsunder

greenhouse conditions using a half-diallel mating design, in addition to

estimating the extent of heterobeltiosis and potence ratio. MATERIALS AND METHODS

This study was conducted at greenhouses of Kaha Vegetable

Reserch Farm, Horticulture Research Institute, Agriculture Research Center

(ARC), Kalubia Governorate, Egypt. Seventy eight accessions of cherry

tomatowere planted in greenhouse duringthe 2012 winter planting for

propagation by selfing. Five accessions of S. lycopersicum var. cerasiforme

and 2 accessions of Solanum sp. were selected based on their characters,

especially productivity and fruit quality (Table 1).A crossing program was

conducted among 7 cherry tomato accession in a half-daillel mating design

(Grriffing, 1956).

Seeds of the 28 genotypes (7 parents + 21 F1's) were sown in

speedling trays filled with mixture of peatmoss and vermiculate (1:1)

enriched with macro and micro elements on mid of August and transplanted

on mid of September 2012 and 2013. A randomized complete block design

(RCBD) with 3 replicates was used. The area of the greenhouse was divided

into 5 beds. Each bed was 1.2 m wide, plants were transplanted on both

sides of the bed. The in-row distance between plants was 50 cm. Each

experimental unit (EU) consisted of ten plants. All cultural practices

(fertilization, irrigation, and controlling weeds, diseases and insects) were

performed as recommended for commercial tomato production in

greenhouse.

58

Table 1. Cherry tomatoaccessionsevaluated. Parent Accession Cultivar name Country Characters

S. lycopersicum var. cerasiforme

P1 LYC 196/81 Bubjekosoko Indeterminate, high set and yield,

red fruit

P2 PI 204981 126-1 US Indeterminate, plant vigor, red

fruit

P3 PI 647522 Cal Red Cherry US,

California

Indeterminate, high set and yield,

dark red fruit

P4 PI 647555 Siten Macedonia Indeterminate, plant vigor, red

fruit

P7 PI 639207 Black Cherry Indeterminate, high set and yield,

pink fruit

Solanum sp.

P5 PI 260402 M-10 Indeterminate, plant vigor, high

yield, sweetness, red fruit P6 PI 126915 125 zAccession: The LYC was the courtesy of the InstitutfürPflanzengenetik und

Kulturpfianzenforschung,Genebank, Gatersleben, Germany and the PIs were kindly provided

by the USDA through Dr. Charles Block (Plant Introduction Station, Ames, Iowa).

Data were recorded on evaluated genotypes on early (EY – the first

three harvests) and total yield (TY – all the collected fruits) per plant, and

fruit quality characters, i.e., average fruit weight (AFW – average weight of

30 fruits of EU), pericarp thickness (FPT - means of 10 fruits of EU), fruit

firmness (FF), and fruit contents of total soluble solids (TSS), titratable

acidity (TAC), ascorbic acid (AAC) and lycopene (LC).

Fruit firmness was determined in 10 red-ripe fruits from each

genotype perEU using a food pressure tester (Force Gauge Model M4-200)

Mark-10 (Series 4). Three readings were taken for each fruit by pushing the

pentameter needle slowly at 3 different sites (near the shoulder, blossom end

and equatorial plane). Then, mean of the 3 readings was calculated. Samples

of 30 ripe fruits (from the third to six clusters) representing each EU were

picked for analysis of fruit analyses. An extract was obtained by blending

and filtering flesh of each fruit sample. TSS was determined using a hand

refractometer. TAC was ascertained using 0.1 N NaOH solution and

phenolphthalein as indicator (AOAC, 1990). AAC (vitamin C) was

measured using 2,6 dichlorophenol indophenol dye (AOAC, 1990).

Statistical analysis

Results of the two years were combined and statistically analyzed

using MSTAT-C v. 2.1 (Michigan State University, Michigan, USA) and

mean comparisons were based on the Duncan's multiple range test (Steel

and Torrie, 1981).

Estimation of heterobeltiosis

Heterobeltiosis (better-parent heterosis - BPH) for the different

studied characters were calculated using the following equation (Mather and

Jinks, 1971):

59

BPH =

S.E=

Where, , mean value of hybrid, mean value of the better parent, S.E.

standard error, MSe mean square of error, and r number of replicates.

Estimation of potence ratio

Potence ratio (P)was used to determine the direction of dominance

according to Smith (1952) as follows:

Where, mean value of the hybrid, mean of the smaller parent,

mean of the larger parent, and MP mid-parent value.

The absence of dominance was assumed when the difference

between the parents was significant and ــــ MP was not significant.

Complete dominance was assumed when P equaled to or did not differ from

±1.0. Meanwhile, partial dominance was considered when P was between

+1.0 and -1.0, but was not equal to zero. Over dominance (Heterosis) was

assumed when P exceeded ± 1.0.

Analyses of combining abilities

When the F-test revealed significant differences among the

genotypes, combining ability analysis was followed. The values of general

combining ability (GCA) and specific combining ability (SCA) were

estimated according to Griffing'smodel 1 method 2 of diallel analysis (Singh

and Choudhary, 1979):

Yij = μ + gi + gj + sij + eijk

Where,Yij is the mean phenotypicvalue, μ is the general mean, gi is the

general combining ability (GCA) effect, sijis the specific combining ability

(SCA) effect and eijkis the error term. Analysis of variance table for combining ability with expectation of

mean square was set up as follows:

Source d.f. M.S. E.M.S.

GCA p-1 Mg SCA p(p-1)/2 Ms Error (r-1)(p-1)

The additive and dominance genetic variances were estimated from the

combining ability components as follows:

Where

Where

60

RESULTS AND DISCUSSION

The present investigation was undertaken to evaluate performance of

cherry tomato accessions, calculate potence ration and extent of

heterobeltiosis and to identify potential parental lines and cross

combinations on the basis of combining ability under greenhouse conditions

in cherry tomato. Twenty-one cross combinations (F1s) along with their 7

parents were evaluated and observations were recorded on fruit yield and

component and fruit quality traits during winter seasons of 2013 and 2014

under greenhouse conditions of Kaha Vegetable Reserch Farm, ARC,

Kalubia Governorate.

Variation and mean performance of parents and hybrids Significant differences were found among the evaluated genotypes

(parents and their hybrids) under greenhouse conditions during 2013 and

2014 winter seasons for all studied characters (Table 2). For yield and its

components traits, LYC 196/81 cv. Bubjekosoko (P1) was the best parents,

as it gave the highest EY and TY (0.88 kg/plant and 6.64 kg/plant,

respectively), followed by PI 647522 cv. Cal Red Cherry (P3 - 0.52 kg/plant

and 4.93 kg/plant, respectively) and PI 639207 cv. Black Cherry (P7) for TY

(5.13 kg/plant). For AFW, P1 have the highest fruit weight followed by P3.

For fruit quality traits, PT was high in P1, P3 and P7. Fruits of PI 204981 cv.

126-1 (P2) and PI 647555 cv. Siten (P4) had more firmness compared with

other parents. Fruit TSS content was higher with PI 260402 cv. M-10 (P5)

and PI 126915 cv. 125 (P6). Parent P7 had the highest content of ascorbic

acid and lycopene. Parent P2 had the highest content of titratable acidity.

For hybrids, the cross P1 × P7 have the highest EY and TY (0.88

kg/plant and 7.61 kg/plant, respectively), while, the cross P1 × P3 have

highly TY, 7.87 kg/plant compared with all evaluated genotypes.Average

fruit weight was higher in hybrid P4 × P7 followed by P1 × P7 and P1 × P3

(22.92, 20.77 and 20.51 g, respectively). For fruit quality traits, some

crosses were superior for the following traits:PT (P3 × P7 and P1 × P3), FF

(P2 × P4), TSS content (P5 × P6, P5 × P7, P6 × P7, and P1 × P5),TAC (P2 × P4,

P2 × P5, P2 × P6, P1 × P2, P1 × P5, P5 × P6, and P4 × P5),AAC(P5 × P6, P4 ×

P7, and P1 × P5), and LC (P6 × P7 and P5 × P7).

Mode of gene action for different characters

The success of a breeding program depends upon the choice of

suitable parents and their utilization by adopting an appropriate breeding

method. The combining ability analysis has been used extensively to

identify potential parents either to be used in the development of hybrids or

recombinant breeding for getting elite pure parents. This analysis facilitates

61

Table 2. Combined mean performance of seven cherry tomato cvs and their

twenty one F1s of various studied characters during the 2012 and

2013 winter plantings.

Po

pu

lati

on

s

Early

yie

ld

(kg

/pla

nt)

To

tal

yie

ld

(kg

/pla

nt)

Av

era

ge f

ru

it

weig

ht

(g)

Peri

carp

thic

kn

ess

(mm

)

Fru

it f

irm

ness

(kg

/cm

2)

TS

S

(%)

Tit

rata

ble

aci

dit

y c

on

ten

t

(mg

cit

ric

aci

d/1

00g

fre

sh

fru

it)

Asc

orb

ic a

cid

co

nte

nt

(mg

/10

0g

fresh

fru

it)

Lyco

pen

e

co

nte

nt

(mg

/10

0g

fru

it)

Parents

P1 0.88 a 6.64 b 24.88 a 3.30 a-c 0.27 g-j 7.33 f-j 0.81 g-i 20.24 h 1.59 n

P2 0.22 g 2.84 k 8.95 mn 2.60 l 0.33 b 5.47 l 1.21 a 20.77 gh 2.01 g-i

P3 0.52 de 4.93 e-i 20.81 c 3.31 a-c 0.27 g-k 7.40 f-i 0.83 g-i 17.32 i 1.68 mn

P4 0.22 g 3.47 jk 6.94 o 2.89 g-k 0.32 bc 6.40 j-l 0.94 c-h 22.79 d-f 1.86 k

P5 0.24 g 4.00 ij 8.62 n 2.81 j-k 0.26 j-l 8.80 a-d 1.04 a-f 24.25 cd 2.05 fg

P6 0.25 g 4.61 e-i 8.50 n 2.85 h-k 0.25 kl 8.00 c-g 0.99 b-h 21.81 e-h 2.18 b-e

P7 0.26 g 5.13 e-g 15.52 e-h 3.39 ab 0.27 g-j 6.93 h-k 0.59 j 25.30 bc 2.30 a

F1 hybrids

P1 × P2 0.58 cd 5.13 e-g 15.01 f-h 2.95 f-j 0.24 l 7.47 f-i 1.10 a-c 20.78 gh 1.88 jk

P1 × P3 0.73 b 7.87 a 20.51 c 3.43 ab 0.26 j-l 7.53 f-i 0.89 d-h 19.98 h 1.74 lm

P1 × P4 0.59 cd 5.22 d-f 14.90 gh 3.01 e-h 0.26 j-l 7.53 f-i 0.99 b-h 21.13 f-h 1.82 kl

P1 × P5 0.64 c 6.06 b-d 15.73 e-g 2.93 f-j 0.22 m 8.73 a-e 1.01 a-g 26.44 ab 1.93 h-k

P1 × P6 0.73 b 6.24 bc 15.16 e-h 2.98 f-i 0.21 m 8.17 b-f 0.95 b-h 22.42 d-g 1.98 g-j

P1 × P7 0.88 a 7.61 a 20.77 c 3.27 b-d 0.30 c-e 7.63 f-i 0.79 hi 25.05 bc 2.09e-g

P2 × P3 0.48 e 4.26 e-j 19.08 d 2.89 g-k 0.25 j-l 6.20 kl 1.08 a-d 22.56 d-f 1.89 i-k

P2 × P4 0.26 g 4.15 h-j 9.60 lm 2.86 h-k 0.35 a 6.17 kl 1.16 ab 20.50 h 2.01 g-i

P2 × P5 0.23 g 3.40 jk 10.96 k 2.56 l 0.26 h-k 7.07 g-k 1.14 a-c 20.41 h 2.09 d-g

P2 × P6 0.36 f 4.36 f-j 11.95 ij 2.85 h-k 0.26 h-l 6.80 i-k 1.13 a-c 22.41 d-g 2.18 b-e

P2 × P7 0.45 e 4.34 f-j 14.57 h 3.01 e-h 0.31 b-d 6.10 kl 0.89 d-h 23.98 cd 2.20 b-d

P3 × P4 0.49 e 4.92 e-i 15.14 e-h 3.02 e-h 0.26 j-l 6.87 i-k 0.95 c-h 24.20 cd 1.92 h-k

P3 × P5 0.49 e 5.11 e-h 14.91 gh 3.00 e-h 0.27 g-k 7.37 f-j 0.68 ij 23.54 c-e 2.01 g-i

P3 × P6 0.44 e 5.50 c-e 16.12 e 3.18 c-e 0.30 c-f 7.73 f-i 0.85 f-i 23.17 de 1.99 g-j

P3 × P7 0.53 de 6.64 b 22.92 b 3.47 a 0.28 e-h 7.80 e-i 0.79 hi 20.31 h 2.07 e-g

P4 × P5 0.28 fg 4.01 ij 11.11 jk 2.73 kl 0.32bc 7.93 d-h 1.05 a-f 20.67 gh 2.03 gh

P4 × P6 0.24 g 4.19 g-j 10.17 kl 2.96 f-j 0.27 g-k 7.53 f-i 0.96 b-h 23.19 de 2.03 gh

P4 × P7 0.28 fg 5.14 e-g 12.73 i 3.11 d-f 0.29 d-g 7.20 f-j 0.82 g-i 26.69 ab 2.15 c-f

P5 × P6 0.36 f 4.59 e-i 10.95 k 2.79 jk 0.24 l 9.13 a 1.06 a-e 27.88 a 2.19 b-e

P5 × P7 0.34 f 4.71 e-i 12.68 i 3.02 e-h 0.26 j-l 9.10 ab 0.86 f-i 22.96 de 2.22 a-c

P6 × P7 0.58 cd 5.38 c-e 15.99 ef 3.06 e-g 0.28 f-i 8.93 a-c 0.83 g-i 20.76 gh 2.37 a zValues followed by a letter in common are not significantly different at the 0.05 level according

to Duncan's multiple range test. yS. lycopersium var. cerasiforme:P1,LYC 196/81cv. Bubjekosoko;P2,PI 204981 cv. 126-1;P3, PI

647522cv. Cal Red Cherry;P4,PI 647555cv. Siten;P7,PI 639207cv. Black Cherry (P7);

Solanumsp. P5, PI 260402 cv. M-10 and P6,PI 126915 cv. 125.

the partitioning of genotypic variation of crosses into variation due to GCA

and SCA. GCA effects are the measure of additive gene action which

represent the fixable components of genetic variance and are used to classify

the parents for the breeding behavior in hybrid combinations. On the other

hand, SCA effects are the measure of non-additive gene action which is

related to non-fixable component of genetic variance (Griffing

1956).Therefore, it is important to assess the general and specific combining

ability effects in the selection of the parents and the formulation of an

appropriate crossing plan. Among the various breeding methods, diallel mating

62

design (method 2) excluding reciprocals (Griffing 1956) has been used in the

present study to evaluate 7 parents and their 21 crosses. Mean squares for genotypes, parents, and hybrids were highly

significant (P ≤ 0.01) for all studied traits (Table 3).The parents versus

hybrids (P vs H) component were highly significant for all studied

characters except pericarp thickness and titratable acidity.

Table 3. Mean squares from analysis of variance of 7 × 7 half diallel crosses of

tomato for various characters.

Character

Mean squares

Rep.

df = 3

Genotype

df =27

Parent (P)

df = 6

Hybrid (H)

df = 20

P vs H

df = 1

Error

df = 54

Early yield 0.0009 0.1186** 0.1871** 0.0955** 0.1721** 0.0019

Total yield 5.1213 4.1519** 4.6127** 4.0098** 6.9285** 0.2489

Average fruit weight 0.9640 63.8377** 149.7887** 39.8100** 28.6871** 0.2910

Pericarp thickness 0.0009 0.1631** 0.2827** 0.1352** 0.0048ns 0.0089

Fruit firmness 0.0001 0.0031** 0.0025** 0.0033** 0.0022** 0.0001

TSS 0.2537 2.6493** 3.4863** 2.4164** 2.2857** 0.2721

Titratable acidity 0.0050 0.0663** 0.1153** 0.0540** 0.0185ns 0.0113

Ascorbic acid content 5.5753 17.0021** 21.4142** 15.6940** 16.6895** 0.9252

Lycopene content 0.0055 0.0977** 0.1970** 0.0672** 0.1138** 0.0037 **

highly significant (Ρ ≤ 0.01) and ns

non-significant.

The analyses of variance for combining ability exhibited highly

significant (P≤0.01) components of GCA and SCA mean squares for most

of the studied characters except PT and lycopene content characters which

were significant (P≤0.05) and also SCA mean square of TA which was non-

significant (Table 4).

Table 4. Analysis of variance for combining ability of a 7 × 7 half diallel

crosses for various characters in tomato.

Characters

Mean squares

δ2g δ2

s δ2e δ2

g : δ2s δ2

A δ2D GCA

df= 6

SCA

df= 21

Error

d = 54

Early yield 0.150** 0.008** 0.001 0.032 0.007 0.001 4.29 0.063 0.007

Total yield 5.291** 0.311** 0.083 1.107 0.228 0.083 4.86 2.214 0.228

Average fruit weight 85.634** 2.892** 0.097 18.387 2.795 0.097 6.58 36.774 2.795

Pericarp thickness 0.222** 0.006* 0.003 0.048 0.003 0.003 14.60 0.096 0.003

Fruit firmness 0.002** 0.001** 0.00005 0.00033 0.00066 0.00005 0.51 0.00067 0.00067

TSS 3.226** 0.214** 0.091 0.669 0.123 0.091 5.44 1.339 0.123

Titratable acidity 0.083** 0.005ns 0.004 0.0175 0.0008 0.004 21.26 0.035 0.0008

Ascorbic acid content 8.139** 4.961** 0.308 0.706 4.653 0.706 0.15 1.413 4.653

Lycopene content 0.223** 0.006* 0.003 0.0482 0.0032 0.003 14.90 0.096 0.003 **

Highly significant (Ρ ≤ 0.01); *significant (P≤0.05);

nsnon-significant.

These results proved that both additive and non-additive gene effects

play an important role in operating the heredity of all studied traits except

TA. Higher values of variance due to GCA (δ2

g) than variance due to SCA

(δ2

s) and δ2

g/δ2

s ratio was more than one for all studied characters, except FF

and AAC, suggesting preponderance of additive gene action for these

63

characters. Meanwhile, higher values of δ2

s than δ2

g and δ2

g/δ2s ratio was

less than one for FF and AAC, indicating that non-additive variance

prevailed in genetic determination of these characters. These results,

accordingly, indicated that cherry tomato crosses can produce F1 hybrids

which may perform better, in one or more traits, than either of their parents

or other commercial cultivars.

Due to the predominance of additive gene action in inheritance of

most yield components and quality traits, recurrent selection, a breeding

method that increases the frequency of favorable alleles and identifies the

superior combinations by repeated crossing and selection could be the best

method to exploit the additive gene effects. The use of diallel selective

mating (Jensen 1970) or mass selection with concurrent random mating

(Redden and Jensen 1974) or restricted recurrent selection by mating the

most desirable segregants followed by selection (Shende et al 2012) might

be useful breeding strategies for the improvement of these traits governed

by both additive and non-additive types of gene action.

Considering the non-additive gene action for the control of FF and

fruit AAC traits, selection will slow genetic improvement. The successful

breeding methods will be those that accumulate the genes to form superior

gene constellations interacting in a favorable manner, such as heterosis

breeding, which is the best possible option for improving these traits in

cherry tomato (Kalloo 1991).

Muttappanavar et al (2014) reported that additive gene effects

appeared more important than non-additive gene effects for some traits of

cherry tomato, i.e., TY, AFW, and PT. Also, Garg et al (2007 and 2008),

Hannan (2007) and Andrade et al (2014) reported that additive gene effects

appeared more important than non-additive gene effects for AFW, EY, TY

and fruit TSS for large-sized tomato. Hosamani (2010) found that the

estimates ratio of GCA variance to SCA variance were higher for PT and

TSS. Meanwhile, the previously presented results concerning AAC

character are in agreement with those obtained by Joshi and Kohli (2006)

and Garg et al (2007 and 2008) who reported the importance of non-

additive gene action in the inheritance of this character in large-sized

tomato.

Heterobeltiosis and potence ratio estimations of F1 hybrids

The discovery of hybrid vigour by Shull (1908) opened a new era in

genetic improvement of crop plants which is now referred to as “heterosis

breeding”. Genetically diverse varieties are the main necessity to observe

heterosis in F1 hybrids (Mole et al 1962). It is an effective tool in improving

the yield and component and quality traits of different crop species.

The percent increase (+) or decrease (-) of a cross over the better

parent was calculated to determine heterotic effects for all traits. Data on

64

estimates of heterosis over the better parent (BPH) for the studied characters

are presented in Table (5).

Table 5. Heterobeltiosis (BPH) percentage and potence ratio (P) estimate for

the studied characters of 21 cherry tomato crosses.

Crossesz Early yield Total yield

Average fruit

weight Pericarp thickness Fruit firmness

BPH (%) P BPH (%) P BPH (%) P BPH (%) P BPH (%) P

P1 × P2 -32.16**

0.08 -24.53**

0.21 -39.69**

-0.24 -10.61**

0.00 -26.92**

-2.25

P1 × P3 -14.51**

0.15 15.69* 2.43 -17.57

** -1.15 4.04 39.00 -8.93

** -8.67

P1 × P4 -30.39**

0.12 -23.28**

0.10 -40.11**

-0.11 -8.89**

-0.44 -22.73**

-1.71

P1 × P5 -25.10**

0.24 -10.96 0.56 -36.78**

-0.13 -11.11**

-0.49 -23.21**

-6.77

P1 × P6 -14.12**

0.52 -8.19 0.61 -39.06**

-0.19 -9.60**

-0.40 -26.79**

-5.61

P1 × P7 3.14 0.98 11.91 2.28 -16.53**

0.12 -1.61 -1.74 7.14* 25.00

P2 × P3 -6.45 0.78 -13.60 0.36 -8.28**

0.71 -12.70**

-0.19 -21.79**

-1.48

P2 × P4 18.18 -23.00 19.53 3.14 7.23 1.64 -1.27 0.75 7.69**

7.00

P2 × P5 -1.41 0.60 -14.99 -0.03 22.50**

13.02 -8.67**

-1.35 -18.97**

-0.80

P2 × P6 44.59**

9.25 -5.60 0.71 33.52**

14.43 0.00 1.00 -20.00**

-0.76

P2 × P7 73.08**

10.50 -15.33 0.31 -6.07* 0.71 -11.21

** 0.04 -6.15

* 0.23

P3 × P4 -5.48 0.81 -0.14 0.99 -27.23**

0.18 -8.77**

-0.40 -19.47**

-1.52

P3 × P5 -4.84 0.82 3.65 1.39 -28.34**

0.03 -9.27**

-0.23 0.83 1.40

P3 × P6 -14.19* 0.46 11.54 4.63 -22.54

** 0.24 -3.83 0.45 10.17

** 4.27

P3 × P7 1.94 1.08 29.43**

15.85 10.14**

1.80 2.26 2.84 4.56 -3.40

P4 × P5 18.31 7.50 0.21 1.03 29.00**

3.97 -5.76* -2.85 -0.53

* 0.94

P4 × P6 -4.05 0.14 -9.18 0.26 19.56**

3.12 2.19 3.71 -14.74**

-0.42

P4 × P7 8.97 2.27 0.10 1.01 -17.93**

0.35 -8.16**

-0.11 -9.47**

-0.38

P5 × P6 45.95**

23.67 -0.61 0.91 27.07**

42.76 -1.99 -1.83 -7.47* -5.90

P5 × P7 32.05* 8.14 -8.12 0.26 -18.27

** 0.18 -10.91

** -0.27 -6.71

* -1.20

P6 × P7 123.08**

49.00 4.84 1.96 3.06 1.14 -9.83**

-0.23 0.61 1.15

Crossesz TSS Titratable acidity

Ascorbic acid

content Lycopene content

BPH (%) P BPH (%) P BPH (%) P BPH (%) P

P1 × P2 0.90 1.14 -7.70 0.45 5.47 1.04 18.03**

0.36

P1 × P3 -5.83 5.00 8.94 11.00 -3.49 0.82 9.33**

2.35

P1 × P4 1.80 1.43 10.67 1.64 -5.89 -0.30 14.68**

0.75

P1 × P5 3.97 0.91 3.06 0.76 11.72**

2.09 21.17**

0.46

P1 × P6 4.70 1.50 -2.72 0.56 2.98 1.78 24.53**

0.33

P1 × P7 3.15 2.50 -0.63 0.75 -1.08 0.90 31.34**

0.41

P2 × P3 -16.22**

-0.24 -10.91 0.31 8.64* 2.04 12.60

** 0.28

P2 × P4 -3.65 0.50 -4.14 0.62 -10.04**

-1.26 0.00 1.00

P2 × P5 -19.70**

-0.04 -5.39 0.24 -15.87**

-1.21 4.15 3.17

P2 × P6 -15.00**

0.05 -6.22 0.30 2.76 2.16 8.29**

1.00

P2 × P7 -12.02 -0.14 -26.24**

-0.03 -5.20 0.42 -4.14 0.34

P3 × P4 -7.21 -0.07 0.18 1.03 6.20 1.52 14.19**

1.70

P3 × P5 -16.29**

-1.05 -34.34**

-2.39 -2.94 0.79 19.35**

0.76

P3 × P6 -3.33 0.11 -14.43 -0.72 6.24 1.61 18.35**

0.24

P3 × P7 5.41 2.71 -4.76 0.67 -19.73**

-0.25 23.41**

0.28

P4 × P5 -9.85 0.28 0.80 1.18 -14.78**

-3.89 -1.14 0.76

P4 × P6 -5.83 0.42 -3.52 -0.40 1.79 1.83 -6.74**

0.08

P4 × P7 3.85 2.00 -13.07 0.30 5.52 2.11 -6.46**

0.33

P5 × P6 3.79 1.83 2.25 2.08 14.94**

3.96 6.83**

1.21

P5 × P7 3.41 1.32 -17.52* 0.19 -9.25

** -3.48 -3.27 0.39

P6 × P7 11.67 2.75 -16.61 0.18 -17.95**

-1.60 3.05 2.17 **Highly significant (Ρ ≤ 0.01) and*significant (P≤0.05). zS. lycopersium var. cerasiforme: P1, LYC 196/81 cv. Bubjekosoko; P2, PI 204981 cv. 126-1; P3,

PI 647522 cv. Cal Red Cherry; P4, PI 647555 cv. Siten; P7, PI 639207 cv. Black Cherry (P7);

Solanumsp. P5, PI 260402 cv. M-10 and P6, PI 126915 cv. 125.

65

The extent of BPH varied from -32.16 to 123.08 for early yield, -

24.53 to 29.43 for total yield, -40.11 to 33.52 for average fruit weight, -

12.70 to 4.04 for pericarp thickness, -26.92 to 7.69 for fruit firmness, -19.7

to 5.41 for fruit TSS, -34.34 to 10.67 for fruit titratable acidity content, -

19.73 to 14.94 for fruit ascorbic acid content, and -6.74 to 31.34 for fruit

lycopene content (Table 5).

The estimates of heterobeltiosis, relative to better parent values

(Table 5) reflected significant effects in desirable directions on 13 F1

hybrids for fruit lycopene content, 6 F1 for average fruit weight, 5 F1 for

early yield, 3 F1 for fruit ascorbic acid content, 2 F1 for total yield, and no

hybrid exhibited significant heterobeltiosis in desired direction over better

parent for pericarp thickness, fruit TSS, and fruit titratable acidity content.

Positive and significant heterosis over standard hybrid variety in

cherry tomato traits has been reported Khereba et al (2011) and also, in

large-sized tomato traits have been reported by many investigators

(Metwally et al 2003, Shalaby 2008, 2012 and 2013, Singh and Asati 2011,

Solieman et al 2013).

The values of dominance estimates illustrated in 21 F1 crosses are

presented in Table (5). Early yield per plant showed that potence ratios

ranged from -23.6 to 49, and they were more than ±1 for nine crosses and

between ±1 in 12 crosses indicating over-dominance and partial dominance,

respectively. Potence ratio of total yield per plant varied from -0.03 to

15.85, and they were more than ±1 for 9 crosses, indicating over-dominance

and between ±1 in 8 crosses, indicating partial dominance. Average fruit

weight expressed over dominance in 8 crosses and partial dominance in 13

crosses. In respect to pericarp thickness, potence ratio ranged from -2.85 to

39, and they were more than ±1 for 7 crosses (over dominance), between ±1

for 12 crosses (partial-dominance), +1 for one cross (complete dominance),

and 0 for one cross (no dominance). In case of fruit firmness, 15 crosses

expressed over dominance and 6 crosses expressed partial dominance.

Regarding fruit TSS content, 11 crosses exhibited over-dominance and 10

crosses exhibited partial dominance. In case of fruit titratable acidity, most

of crosses exhibited over-dominance, while 3 crosses exhibited only partial

dominance. Potence ratio of fruit ascorbic acid content expressed over-

dominance in 15 crosses except 6 crosses, where partial dominance was

noticed. Fruit lycopene content character expressed over dominance in 5

crosses, complete dominance in two crosses and partial dominance in 14

crosses.

In cherry tomato, mere breeding for enhanced yield is not important

unless it is qualified by the quality requirements desired by the consumers.

The positive values of heterobeltiosis and potence ratio for the characters

EY, TY, AFW, AAC, and LC reflected the presence of various degrees of

dominance; i.e., partial- to over-dominance which are involved in the

66

inheritance of these characters. Both dominant and additive gene effects

were reported in regulating the inheritance of EY, TY, AFW, and LC with

prevalence of dominance gene effect (Hannanet al 2007). Garg et al (2007

and 2008) illustrated that additive gene effects were found to be more

important than non-additive gene effects in the inheritance of AFW, EY,

TY, FF, PT and TSS. Hence, hybrid breeding can be used efficiently to

improve yield together with quality in tomato (Hannanet al 2007).

Identification of good general and specific combiners

No single parent was found to be a good general combiner for all

studied characters. However, parent P7 exhibited significant GCA effects in

desired direction in most of the heterotic crosses for TY, AFW, PT, FF, fruit

AAC and LC, and was considered as a good general combiner (Table 6).

Next to P7, significant GCA effects in desired direction for EY, TY, AFW,

PT and fruit TSS was shown by P1 and P3. Therefore, three parents P7, P1,

and P3 could be picked up as potential donors for fruit yield per plant and

other important horticultural traits. Parent P5 exhibited highly significant

GCA effects in desired direction for fruit contents of TSS, TA, AAC and LC

traits. Therefore, this parent could be selected as potential donor for fruit

quality traits.

Table 6. General combining ability (GCA) effects of 7 parents for different

characters of cherry tomato in a 7 × 7 half diallel cross.

Parent Early

yield

Total

yield

Average

fruit

weight

Pericarp

thicknes

s

Fruit

firmness TSS

Titratable

acidity

Ascorbic

acid

content

Lycopene

content

P1 0.26** 1.25** 4.01** 0.12** -0.02** 0.21** -0.02ns -0.46** -0.17**

P2 -0.09** -0.98** -1.85** -0.19** 0.02** -1.01** 0.15** -0.92** 0.02**

P3 0.07** 0.45** 3.84** 0.17** -0.003ns -0.17ns -0.07** -1.34** -0.13**

P4 -0.11** -0.62** -3.14** -0.07** 0.02** -0.42** 0.03ns 0.17ns -0.05**

P5 -0.09** -0.47** -2.47** -0.16** -0.01** 0.79** 0.04** 1.11** 0.05**

P6 -0.04** -0.07ns -2.05** -0.06** -0.01** 0.5** 0.03ns 0.33ns 0.11**

P7 -0.0004ns 0.44** 1.66** 0.18** 0.01** 0.09ns -0.15** 1.10** 0.17**

S.E. (gi) ±0.008 ±0.089 ±0.096 ±0.017 ±0.002 ±0.093 ±0.019 ±0.171 ±0.011

S.E. (gi - gj) ±0.012 ±0.136 ±0.147 ±0.026 ±0.003 ±0.142 ±0.029 ±0.262 ±0.017 **Highly significant (Ρ ≤ 0.01); *significant (P≤0.05); nsnon-significant. zS. lycopersium var. cerasiforme: P1, LYC 196/81 cv. Bubjekosoko; P2, PI 204981 cv. 126-1; P3,

PI 647522 cv. Cal Red Cherry; P4, PI 647555 cv. Siten; P7, PI 639207 cv. Black Cherry;

Solanumsp. P5, PI 260402 cv. M-10 and P6, PI 126915 cv. 125.

SCA involves non-additive effects and additive × dominance and

dominance × dominance interactions, which are non-fixable or non-heritable

and are of significance in hybrid breeding only. So, SCA effects are useful

to predict the potential of a particular cross in exploiting heterosis (Moore

and Currence 1950). Similarly, no single cross was judged as good specific

combiner for all studied characters (Table 7). The cross P1 × P7 exhibited

highly significant SCA effects for EY, TY, AFW, FF, AAC and LY in

desired directions. Also, three crosses exhibited highly significant SCA

effects in desired direction of TY, in addition to PT and FF in cross P2 × P4;

67

to AFW and PT in cross P3 × P7; and to PT in cross P1 × P3 (Table 7).

Moreover, the cross P6 × P7 exhibited significant SCA effects in desired

direction of EY, AFW, FF, TSS and LC. According to the performance of

the hybrid P1 × P7 it was found to be the highest for EY and TY per plant

and one the best genotypes for some quality traits (Table 2); therefore, it

could be identified as potential specific combiner for certain important

traits.

Table 7. Specific combining ability (SCA) effects for different

characters of tomato in 21 crosses.

Character Early

yield

Total

yield

Average

fruit

weight

Pericarp

thickness

Fruit

firmness TSS

Titratable

acidity

Ascorbic

acid

content

Lycopene

content

P1 × P2 -0.04*

-0.16 -1.62**

0.01 -0.03**

0.79**

0.02 -0.40 0.01

P1 × P3 -0.05* 1.15

** -1.81

** 0.13

** 0.005 0.01 0.04 -0.78 0.02

P1 × P4 -0.003 -0.44* -0.44 -0.06 -0.02

** 0.26 0.03 -1.13

* 0.03

P1 × P5 0.02 0.26 -0.28 -0.04 -0.03**

0.25 0.05 3.24**

0.03

P1 × P6 0.07**

0.05 -1.27**

-0.09* -0.03

** -0.02 0.01 -0.01 0.02

P1 × P7 0.17**

0.90**

0.63* -0.05 0.04

** -0.15 0.02 1.85

** 0.07

*

P2 × P3 0.05* -0.23 2.63

** -0.10

* -0.03

** -0.10 0.05 2.26

** -0.01

P2 × P4 0.01 0.73**

0.12 0.11* 0.04

** 0.12 0.03 -1.31

** 0.03

P2 × P5 -0.04* -0.16 0.81

** -0.09

* -0.01

* -0.19 0.01 -2.34

** 0.01

P2 × P6 0.04* 0.39 1.38

** 0.09

* -0.01

* -0.17 0.01 0.44 0.04

P2 × P7 0.09**

-0.13 0.30 0.01 0.01* -0.46

* -0.05 1.24

** -0.004

P3 × P4 0.08**

0.08 -0.03 -0.10* -0.03

** -0.02 0.05 2.81

** 0.08

**

P3 × P5 0.06**

0.12 -0.93**

-0.02 0.01* -0.73

** -0.23

** 1.22

** 0.07

*

P3 × P6 -0.03 0.11 -0.14 0.06 0.04**

-0.07 -0.05 1.62**

-0.006

P3 × P7 0.01 0.74**

2.95**

0.10* 0.003 0.40 0.07 -2.01

** 0.01

P4 × P5 0.03 0.08 2.25**

-0.06 0.03**

0.09 0.04 -3.16**

0.01

P4 × P6 -0.06**

-0.14 0.88**

0.08 -0.01* -0.02 -0.04 0.14 -0.04

P4 × P7 -0.05* 0.30 -0.26 -0.01 -0.01

* 0.05 0.003 2.87

** 0.01

P5 × P6 0.04* 0.11 0.99

** 0.001 -0.01

* 0.37 0.06 3.88

** 0.02

P5 × P7 -0.02 -0.27 -0.98**

-0.01 -0.01* 0.74

** 0.03 -1.81

** -0.02

P6 × P7 0.18**

-0.004 1.91**

-0.07 0.01* 0.87

** 0.01 -3.23

** 0.07

*

S.E. (sii) ±0.019 ±0.220 ±0.238 ±0.042 ±0.005 ±0.230 ±0.047 ±0.424 ±0.027

S.E. (sij–sik) ±0.033 ±0.384 ±0.415 ±0.073 ±0.009 ±0.402 ±0.082 ±0.740 ±0.047

S.E. (sij – skl) ±0.031 ±0.359 ±0.388 ±0.068 ±0.008 ±0.376 ±0.077 ±0.693 ±0.047 **

Highly significant (Ρ ≤ 0.01); *significant (P≤0.05); non-significant.

zS. lycopersium var. cerasiforme: P1, LYC 196/81 cv. Bubjekosoko; P2, PI 204981 cv.

126-1; P3, PI 647522 cv. Cal Red Cherry; P4, PI 647555 cv. Siten; P7, PI 639207 cv.

Black Cherry; Solanumsp. P5, PI 260402 cv. M-10 and P6, PI 126915 cv. 125.

CONCLUSION

Results indicated that cherry tomato varieties can be developed

through hybridization. Traits that presented additive gene effects such as

early and total yield per plant, average fruit weight, pericarp thickness and

fruit contents of TSS, titratable acidity and lycopene may be improved by

selection provided there is sufficient genetic variability in the germplasm.

Meanwhile, fruit firmness and ascorbic acid content traits may be improved

by heterosis breeding as these were predominantly governed by non-

additive gene action. No particular evaluated parental cultivar could be used

68

to evaluate all studied traits with equal efficiencies. However, the results

indicated that the most promising combiners for fruit yield along with good

horticultural traits were found to be of P1 (LYC 196/81cv. Bubjekosoko), P3

(PI 647555 cv. Siten) and P7 (PI 639207 cv. Black Cherry), and they could

be used further in cherry tomato hybridization programs. The best hybrid

combination was found to be of P1 × P7for yield and fruit quality. Partial- to

over-dominance reactions for the inheritance of fruit yield and other

economic important traits have been realized.

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التحميل الوراثى إليجاد أنسب اآلباء لتطوير ىجن طماطم كريزية تحت ظروف الصوب

2و أحمد عبداليادى سيد أحمد اإلسالمبولى 1أحمد محمد عمى محمود مركز البحوث الزراعية –معهد بحوث البساتين 2جامعة القاهرة و –كمية الزراعة –قسم الخضر 1

ل التربية لقوة اليجين، التى يستفاد منيا فى تطوير توافيق يمكن تحسين الطماطم الكريزية من خال لتقدير قوة اليجين مقارنة بأحسن اآلباء، و درجة السيادة، و القدرة عمى 7× 7مرغوبة. نظم برنامج تيجين دائرى

صفات فى الطماطم الكريزية.كان التأثير اإلضافى لمجين واضح لكل الصفات 9التوافق و فعل الجين لنحو لمدروسة، عدا صفتى صالبة الثمار و محتواىامن حامض األسكوربيك حيث كانا تحت سيطرة التأثير غير اإلضافى ا

لمجين. عموماً، لم يكن ىناك اب او ىجين معين يمكن استخدامو لتقييم الصفات المدروسة بنفس الكفاءة. لكن، فيما PI 647522 cv. Cal Red( ،و الثالث )LYC 196/81 cv. Bubjekosokoبين اآلباء، كان اآلباء األول )

Cherry( و السابع ، )PI 639207 cv. Black Cherry أفضل اآلباء ذات القدرة عمى التآلف لصفات )المحصول و مكوناتو و بعض صفات الجودة لمثمار، و لذا يمكن استخداميم فى برامج التيجين، أيضاً، أظير األب

تأثير عالى المعنوية لمقدرة العامة عمى التألف فى اإلتجاه المرغوب لصفات ( PI 260402 cv. M-10الخامس )محتوى الثمرة من المواد الصمبة الذائبة الكمية، و الحموضة المعايرة، و حامض األسكوربيك، و الميكوبين.

التألف لصفات األب السابع قيماموجبة عالية المعنويو لتأثيرات القدرة الخاصة عمى× أظيرالتيجين األب األول المحصول و بعض صفات الجودة لمثمار، و ذلك كان متوافقا مع نتائج تقييم اليجن المنتجة مع آبائيم. يمكن

األب السابعكأفضل التوافيق لصفات الجودة ( × PI 126915 cv. 125استغالل التيجين األب السادس )لسيادة )سيادة جزئية إلى سيادة متفوقة( لمصفات لمثمار.يعكس المظير العام لميجن المنتجة درجات محتمفة من ا

المدروسة، أظيرت بعض اليجن قوة ىجين معنوية فى اإلتجاه المرغوب لمصفات المقيمة.

(1795) 07 -55( : 9)91المجلة المصرية لتربية النبات