Mycorrhizal Fungi for Improved Soil Fertility and Plant Health
(or “Management and Utilization of Arbuscular Mycorrhizal Fungi”)
David DoudsUSDA-ARS Eastern Regional Research [email protected]
Introduction Structure Function
Management of AM fungi
On-farm production and utilization of inoculum
Field trials
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
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
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
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
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
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
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)
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