Mycorrhizal Fungi for Improved Soil Fertility and Plant Health

(or “Management and Utilization of Arbuscular Mycorrhizal Fungi”)

David DoudsUSDA-ARS Eastern Regional Research Centerdavid.douds@ars.usda.gov

Introduction Structure Function

Management of AM fungi

On-farm production and utilization of inoculum

Field trials

Arbuscular Mycorrhizal [AM] fungi Arbuscule

(L. “small tree”)

Mycorrhiza (Gr. “fungus root”)

- exudate + exudate

Development of an arbusculeKinden and Brown, 1979

Function of mycorrhizas

Green ash (Fraxinus pennsylvanica)

Other benefits

To the plant: Enhanced water relations Enhanced pest resistance

To the soil: Stability of soil aggregates (glomalin)

How does the AM fungus benefit?AM fungi are “obligate symbionts” They must live in symbiosis with plants to

complete their life cycles Why?

Metabolic division of labor among the structures of the fungus

Only the fungus within the root can absorb sugars for energy and make lipids necessary for storage and growth

Germinating spores can only grow as long as their stored lipids hold out

How can we take advantage of the AM symbiosis in agriculture?

1. Manage the AM fungi indigenous to the soil (row crop farms)

2. Inoculate with effective isolates (horticulture crops, vegetable farms, labor intensive farms)

I. Farm management practices that influence indigenous AM fungi

Fertilization Pesticide application Over wintering cover crops Crop rotation Tillage Farming System

Cooperative research with The Rodale Institute

1. Over wintering cover crops Used for:

Erosion control Nutrient management Organic matter Weed management

Fringe benefit: Build populations of AM

fungi Function as a ‘mini’

crop rotation

Over wintering crop of hairy vetch increased the AM fungus inoculum present in the soil

Long fallow disorder

Similar to bare fallows: Flooded soil syndrome Stale weed seed bank treatments

2. Crop rotation Some AM fungi are more

prolific when grown with a particular host plant

The AM fungi most prevalent after growth of one crop may not be the ones most beneficial to that crop

AM fungi may play a role in yield decline characteristic of continuous monoculture

Implications for a big switch to continuous corn for ethanol production?

3. Tillage Tillage interferes with

two functions of the extraradical mycelium of AM fungi:

1. As infective propagules

2. As nutrient absorbing organs of the symbiosis

Fairchild and Miller, 1990

1 2 30.3

0.4

0.5

0.6

0.7

0.8

0.9UndisturbedDisturbed

No added P

Cycle

Sh

oo

t d

ry w

t (g

)

1 2 30.4

0.5

0.6

0.7

0.8

0.9

+ 160 µgP g-1 Soil

Cycle

Sh

oo

t d

ry w

t (g

)

a. Corn grown for 4 wks in inoculated soil

b. Harvest shoot only

c. Disturb soil in half of pots, replant

d. Repeat cycle

6. Farming system The Farming Systems Trial®

Soils from the organic rotations have a higher AM fungus inoculum potential

… and greater spore populations

Largely due to the over wintering cover crops, the organic farming systems have live plant cover 70% of the year vs. 40% for the conventional farming system.

II. Inoculation with AM fungi

Options:commercially available inoculaproduce it yourself

Target farmers:vegetable producers who grow their own seedlings

labor intensive farms

On-farm inoculum productionMaterials

compostvermiculitegrow bags

Transplant:Bahiagrass (Paspalum notatum) seedlingsprecolonized by AM fungi

Weed and water for one growing season (remove flowers in mild climates)

Inoculum is ready for use the following spring

Details in the web article on the handout

Considerations Introduce pathogens?

Compost has pathogen suppressive qualities Bahiagrass unlikely to share pathogens with

eventual crop host

Introduce weeds? Bahiagrass is frost killed (temperate climates) Some weeds are present in the compost

Functional diversity of AM fungi

7 gallon “grow bags”

Inoculum of AM fungi

Spores

Infective hyphae

Colonized roots

Production of propagules of AM fungi in 1:4 [v/v] mixtures of yard clippings compost and vermiculite. Results of MPN bioassays.

Inoculated PropagulesAM fungus cm-3 bag (x106)

Glomus 120 2.4mosseae

Glomus 750 15.0etunicatum

Glomus 120 2.4geosporum

Glomus 365 7.3claroideum

Spore production varies with dilution

Modifications to on-farm inoculum production system

Propagate indigenous isolates of AM fungi Add field soil to compost+ vermiculite mix Pre-inoculate bahiagrass with field soil

Use of alternate “inert” diluents Horticultural potting media Perlite

Modifications to on-farm system

Diluents Field soil

Means of 3 years

0 10 20 30 40 50 60 70 800

20

40

60

80

100

Conv

Legume

Manure

Soil Depth

Pro

pag

ule

s cm

-3

Where to collect the soil- top 2-4 inches

Rodale Farming Systems Trial

Utilization of inoculum in the greenhouse

Goal: produce a well-colonized seedling via organic practices, of comparable size to a conv.-grown seedling.

Manipulation of media, N P availability

Response of colonization to P level for tomato, pepper, and bahiagrass

0 10 20 30 40 50 60 700

10

20

30

40

50

60

70Tomato (Crista)

Pepper (Lafayette)

Bahiagrass

P concentration (ppm)

Ro

ot

len

gth

co

lon

ize

d (

%)

How does this happen? Roots growing in high P exude less of the

hyphal branching signal This leads to less new colonization

Roots release less sugar to the fungus already within the root This leads to less spread of colonization

Less carbohydrate supplied to the fungus This leads to decreased spore production

An important factor for the utilization of AM fungi in the greenhouse

Organic media experiment1. Conventional (Premier pro mix +

Hoag (0.31 ppm P) 3X /wk)Rodale potting mix (20% compost)

2. No N addition3. + Blood Meal (add all at once, 9 g/flat)4. + Fish (added 3X /wk)

Sunshine Mix #1 (SunGro Horticulture)5. No N addition6. + Blood Meal (add all at once)7. + Fish (added 3X /wk)

Results with leek cv. Musselburgh Shoot wt (g) Shoot %P Colon %Conv 0.09 c 0.15 c 27.7 abRodale

0 N 0.08 c 0.35 ab 27.8 abBM 0.25 a 0.40 ab 3.2 c Fish 0.16 abc 0.42 a 16.6 bc

Sunshine0 N 0.12 bc 0.36 ab 34.2 aBM 0.19 ab 0.29 b 5.7 cFish 0.19 ab 0.33 ab 16.2 bc

Follow-up experiment

Leek cv. Musselburgh in the growth chamber

Single addition of blood meal did not inhibit early colonization, but inhibited subsequent spread of colonization.

0 1 2 3 40

10

20

30

Blood Meal 3x/wkBlood Meal To

Hoag -P

A

Co

lon

iza

tio

n (

% r

oo

t le

ng

th)

0 1 2 3 40

6

12

18

24

30

36

B

Co

lon

ize

d r

oo

t le

ng

th (

cm

)

0 1 2 3 40

5

10

15

20

25

30

35

C

Weeks

Infe

cti

on

Un

its

Tomato cv. BHN 589

ANOVA (full model Pr>F)Myc 0.2404 <0.0001Tmt <0.0001 <0.0001M X T <0.0001 <0.0001

Treatment Shoot Dry Wt Colon(g) (%)

Nonmycorrhizal1. Conv 0.68 ± .04 0

Rodale Mix2. 0 N 0.52 ± .03 03. Blood meal 0.92 ± .06 04. Fish 0.87 ± .09 0

Sunshine Mix5. 0 N 0.12 ± .01 06. Blood Meal 0.18 ± .05 07. Fish 0.17 ± .02 0

Treatment Shoot Dry Wt Colon (g) (%)Mycorrhizal1. Conv 0.62 ± .03 15.0 ± 1.2

Rodale Mix2. 0 N 0.27 ± .02 6.7 ± 1.33. BM 1.00 ± .08 3.7 ± 0.84. Fish 0.76 ± .03 10.3 ± 2.0

Sunshine Mix5. 0 N 0.11 ± .01 1.2 ± 0.66. BM 0.57 ± .03 5.3 ± 1.47. Fish 0.34 ± .05 8.4 ± 1.4

Pepper cv. Revolution

ANOVA (full model Pr>F)Myc <0.0001 <0.0001Tmt <0.0001 0.6185M X T <0.0001 0.6185

Nonmycorrhizal

1. Conv 0.39 ± .02 0

Rodale Mix2. 0 N 0.25 ± .02 03. BM 0.79 ± .05 04. Fish 0.56 ± .04 0

Sunshine Mix5. 0 N 0.13 ± .01 06. BM 0.36 ± .04 07. Fish 0.21 ± .02 0

Mycorrhizal

1. Conv 0.31 ± .024 2.0 ± 0.5

Rodale Mix2. 0 N 0.22 ± .01 1.8 ± 0.83. BM 0.57 ± .06 1.8 ± 0.64. Fish 0.34 ± .05 1.5 ± 0.5

Sunshine Mix5. 0 N 0.09 ± .01 2.2 ± 0.76. BM 0.42 ± .01 2.1 ± 0.37. Fish 0.19 ± .02 0.8 ± 0.3

Pepper cv. Revolution yield (Rodale)

ANOVA (full model Pr>F)Myc 0.7162Tmt 0.2565M X T 0.7484

Nonmycorrhizal kg/plant1. Conv -

Rodale Mix2. 0 N 1.59 ± .273. Blood meal 1.61 ± .104. Fish 1.73 ± .12

Sunshine Mix5. 0 N 1.48 ± .256. Blood Meal 1.39 ± .147. Fish 1.59 ± .24

*The average yield/plant at local conv. farm= 1.4 - 1.7 kg/plant

Mycorrhizal kg/plant1. Conv -

Rodale Mix2. 0 N 1.49 ± .183. Blood meal 1.74 ± .164. Fish 1.74 ± .14

Sunshine Mix5. 0 N 1.25 ± .166. Blood Meal 1.59 ± .07. Fish 1.80 ± .10

Pepper cv. Revolution yield (conv)

ANOVA (full model Pr>F)Myc 0.0394Tmt 0.7928M X T 0.4314

Nonmycorrhizal kg/4plants1. Conv 7.39 ± 1.07

Rodale Mix2. 0 N 8.04 ± .763. Blood meal 7.21 ± .794. Fish 6.65 ± .91

Sunshine Mix5. 0 N 5.61 ± .966. Blood Meal 6.64 ± 1.147. Fish 6.93 ± 1.12

Mycorrhizal kg/4plants1. Conv 8.48 ± .79

Rodale Mix2. 0 N 7.00 ± 1.133. Blood meal 7.33 ± .804. Fish 8.08 ± .42

Sunshine Mix5. 0 N 7.77 ± .466. Blood Meal 9.43 ± .737. Fish 7.54 ± 1.11

Tomato cv. BHN (Rodale)

ANOVA (full model Pr>F)

Myc 0.9374 0.7956Tmt 0.0324 0.7435M X T 0.8615 0.5358

Treatment Mkt Term (kg/2 pl)

Nonmycorrhizal1. Conv - -

Rodale Mix2. 0 N 1.9 ±.2 7.6 ±.33. Blood meal 2.8 ±.5 8.9 ±.54. Fish 2.9 ±.4 6.9 ±.8

Sunshine Mix5. 0 N 1.7 ±.3 7.3 ±.76. Blood Meal 2.9 ±.7 6.5 ±.747. Fish 2.4 ±.4 7.7 ±.9

Termination after 5 harvests due to late blight.

Treatment Mkt Term (kg/2 pl)

Mycorrhizal 1. Conv - -

Rodale Mix2. 0 N 2.4 ±.6 6.8 ±.73. Blood meal 2.2 ±.3 7.5 ±.54. Fish 3.1 ±.4 8.1 ±.9

Sunshine Mix5. 0 N 1.6 ±.5 6.9 ±.56. Blood Meal 3.0 ±.3 7.6 ±1.47. Fish 2.2 ±.4 7.3 ±1.1

Tomato cv. BHN yield (conv. farm)

ANOVA (full model Pr>F)Myc 0.3353Tmt 0.2038M X T 0.4535

Treatment Marketable (kg/3 plants)

Nonmycorrhizal

1. Conv 15.5 ± 2.3

Rodale Mix2. 0 N 15.4 ± 1.73. Blood meal 16.5 ± 1.64. Fish 15.8 ± 1.4 Sunshine Mix5. 0 N 14.9 ± 1.66. Blood Meal 20.7 ± 2.67. Fish 19.5 ± 1.5

No early termination

Mycorrhizal

1. Conv 19.8 ± 1.2

Rodale Mix2. 0 N 18.2 ± 2.23. Blood meal 16.3 ± 1.34. Fish 18.0 ± 0.9

Sunshine Mix5. 0 N 15.6 ± 1.26. Blood Meal 18.0 ± 1.67. Fish 18.5 ± 1.9

Using the inoculum in the field General

considerations: Responsiveness of

the plant Health of the

background population of AM fungi

Available Phosphorus level in the soil

Mustards, spinach are not mycorrhizal

Generally inversely proportional to the fineness of the roots

Hard to measure Critical level >50

ppm, but varies

Health of background AM fungus population

Is this inoculum effective?

Control MYKE On-farm0

100

200

300

400

500

600

700Conventional

Compost

Yie

ld (

g p

er

pla

nt)

Potatoes 2002

cv. Superior

Total yield of potatoes- 2003

Control MYKE OF-YCC OF-DMLC0

200

400

600

800

1000

1200

1400CompostConventional

Treatment

Yie

ld (

g p

er 3

pla

nts

)

Potatoes Yield (kg per 4m row)

Cultivar Mycorrhizal Nonmycorrhizal Response

Red Norland 6.1 ± 0.5 4.9 ± 0.2 24%Red Gold 9.5 ± 0.3 8.5 ± 0.2 12%Blue 6.0 ± 0.2 5.4 ± 0.7 12%Yukon Gold 4.9 ± 0.3 5.0 ± 0.4 -0.9%

Somerton Tanks Farm, Philadelphia, PA 2005

Strawberry (cv. Chandler)

Yield (kg per 10 plant subplot) Response

Mycorrhizal Nonmycorrhizal

5.50 ± 0.15 4.71 ± 0.32 17%

Shenk’s Berry Farm, Lititz, PA 2005

Tomatoes Yield (kg per 4 plant subplot)

Cultivar Mycorrhizal Nonmycorrhizal Response

Daybreak 24.1 ± 0.8 26.5 ± 0.9 -9%Empire 30.0 ± 1.1 30.0 ± 1.7 0%Florida 22.9 ± 1.1 20.3 ± 0.6 12%

(kg per bed)San Marzano 156.1 ± 9.2 154.1 ± 11.9 2%

Eagle Point Farm, Kutztown, PA and Covered Bridge Farm, Oley, PA 2005

Yield response of bell peppers, Eagle Point Farm, Kutztown PA

Cultivar 2005 2006 2007 2008 2009 2010 2011

Boynton Bell 10.7 11.4 -0.05 14.0 9.4Colossal 3.4 24.7 0.7 8.4Delirio 15.4Green Puffin -1.3King Arthur 10.7Lafayette 8.1 -6.4 -1.0 3.5 -7.0 -8.0 9.6Orange Sun 0.2Queen -1.2Revolution -3.1 -0.3 8.1Valencia 3.3 6.5 -1.9 12.0 11.9Whopper -0.7 -5.1X3R Red Knight 7.7X3R Wizard 1.1 -2.1 10.2 6.0____________________________________________________________________________1Mycorrhizal Yield Response= 100% x ((Myc-Nonmyc)/Nonmyc)

Leeks cv. Lancelot Shenk’s Berry Farm 2009

Inoculation of sweet potatoes with AM fungus inoculum produced on-farm

Inoculation method Inoculum into

planting hole 2009, 2010

Inoculate potting media and grow in GH for 2 wks

2012, 2013

Sweet potatoes, cv. Beauregard YEAR % increase2009 14.32010 9.12012 6.52013a 7.9*2013b 7.7*

*= cv. Covington