Management and Utilization of Arbuscular Mycorrhizal Fungi

David DoudsUSDA-ARS Eastern Regional Research Center

david.douds@ars.usda.gov

Introduction Structure Function

Management of AM fungi

On-farm production of inoculum

Field trials

Arbuscular Mycorrhizal [AM] fungi Arbuscule

(L. “small tree”)

Mycorrhiza (Gr. “fungus root”)

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 Enhanced salt stress resistance

To the soil: Stability of soil aggregates (glomalin)

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. Fertilization: effect of high nutrient addition upon the fungus (colonization and sporulation)

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 (

%)

2. Pesticide application

Fungicides- direct negative effects upon AM fungi, e.g. Benomyl

Herbicides- indirect effect via removal of potential host plants Diversity of AM fungus community parallels

diversity of the plant community Less carbon available for growth/reproduction

3. 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

Other situations related to bare soil Flooded soil syndrome Stale weed seed bank treatments Long term bare fallow

4. 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?

5. Tillage Tillage interferes with

two functions of the extraradical mycelium of AM fungi:

1. As infective propagules

2. As the nutrient uptake organ

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:a. commercially available inoculab. produce 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

Inoculum is ready for use the following spring

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 section (x106)

Glomus 120 13.5mosseae

Glomus 750 84.4etunicatum

Glomus 120 13.5geosporum

Glomus 365 41.1claroideum

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

Is this inoculum effective?

Considerations for inoculum utilization Factors influencing response to

inoculation: Responsiveness of the plant Soil available P level (> 50ppm) Vigor/ health of the indigenous population of

AM fungi

The goal is to outplant a seedling with a functioning symbiosis already in place

Control MYKE On-farm0

100

200

300

400

500

600

700Conventional

Compost

Yie

ld (

g p

er

pla

nt)

Potatoes 2002

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

Leeks Shenk’s Berry Farm 2009

Sweet potatoes, cv. Beauregard

YEAR % increase2009 19.22010 9.42012 7.02013 8.22014 7.1

Avg 9.8

Eagle Point Farm, Kutztown, PA

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 9.4 Colossal 3.4 24.7 0.7 8.4 Delirio 15.4 Green Puffin -1.3 King Arthur 10.7 Lafayette 8.1 -6.4 -1.0 3.5 -7.0 -8.0 9.6 Orange Sun 0.2 Queen -1.2 Revolution -3.1 -0.3 8.1 Valencia 3.3 6.5 -1.9 12.0 11.9 Whopper -0.7 -5.1 X3R Red Knight 7.7 X3R Wizard 1.1 -2.1 10.2 6.0 ____________________________________________________________________________ 1Mycorrhizal Yield Response= 100. (Myc-Nonmyc)/Nonmyc.