Effects of mixed species cover

crop on tomato biomass and

plant disease suppression

Presenter: Emily Nguyen1

Brian B. McSpadden Gardener2 and Sun-Jeong Park2

Department of Biological Science, California State University

of Fullerton, Fullerton CA

Department of Plant Pathology, OARDC, The Ohio State

University, 1680 Madison Ave, Wooster OH

1

Introduction

• To get certified as organic farming, farmers can not

apply chemicals up to 3 years.

• Cover crops rotation can increase microbial diversity &

organic matter (Schonbeck and Morse, 2006).

• Benitez el al. (2009)

oMixed hay soil increase tomato biomass & disease

suppression.

oMitsuaria & Burkholderia, 2 novel biocontrol

bacteria were isolated from mixed hay soils.

2

Intro (cont.)

Cover

Crop

Planting

time

Mature

time

Benefits

Radish Early

Spring

Late

summer

NR= take up and holds soluble soil

nitrogen

B= harbors beneficial insects

TS= conditions, mellow top soil

Winter

Rye

Fall May NR= takes up and holds soluble soil

nitrogen

K= makes soil potassium more available

Hairy

Vetch

Early fall May N= fixed nitrogen

B= harbor beneficial insects

P= make soil phosphorous more available

3

Schonbeck and Morse (2006)

Table 1: Benefits of some cover crops to soil. Letters in bold indicate a strong effect.

4

Winter Rye Hairy Vetch

Intro. (cont.)

Winter rye and hairy vetch cover crops were photographed in May, 2011.

Objectives and hypothesisObjectives:

1) To compare effects of mixed vs. single species

cover crops on tomato biomass &

2) Compare effects of mixed vs. single species on

plant disease suppression

3) To isolate bacteria associated with plant disease

suppression & mixed species cover crops.

Hypothesis:

Mixed cover crops contribute to higher tomato

biomass and less disease symptom than single

cover crops. 5

Methods

6

Experimental DesignRandomized Complete Block

Mixed Hay, Rye+Vetch

Radish, Rye, & Vetch

East Badger, Fry (compost),

& Fry A

1) Soil fertility test

% organic matter & P

2) Fresh shoot biomass

above ground shoot

weight

3) Bacteria collection

~ 8000 bacteria isolates from

rhizosphere (1/2 R2A, ½ R2A+ Root

extract, 1/3 King’s Medium B, &

Leptothrix strain

Whole cell PCR

Pathogen

inoculation

108 Xanthomonas

cells/ml on 1

leaflet

7

Fig. 1: % Organic Matter

Results_ Soil fertility

No significant difference of cover crops on % organic matter

8

Fig. 2: Extractable Phosphate analysis from soil

Results_ Soil fertility

No significant difference of cover crops on P

Results_ fresh shoot weight

Fig. 3: Fresh shoot tomato biomass in July, 2011.

Field

Cover Crop

FryAF

ry

East

Bad

ger

Vet

ch

Rye

Vet

chRye

Rad

ish

Mix

ed hay

Vet

ch

Rye

Vetc

hRye

Rad

ish

Mix

ed h

ay

Vet

ch

Rye

Vet

chRye

Radi

sh

Mix

ed h

ay

1800

1600

1400

1200

1000

800

600

400

200

Fre

sh

sh

oo

t b

iom

ass,

g

9Plants from mixed hay soil have more fresh shoot weight

Results_ % disease symptoms

10

Fig. 4: Ranking score of percentage disease symptoms

Less disease symptom plants from rye + vetch soil,

significantly 1/3 fields

11

NC

WC PC

DNA PCDNA PC

WC PC

Mitsuaria_H24L5 Burkholderia_R2F4

Samples spiked with 6ul

of R2F4 DNA

100bp L

~450 bp

500400

Fig. 5: Optimization of Mitsuaria and Burkholderia screening PCR.

Results_ Double freeze/thaw whole cell PCR

Burkholderia side, bands matched with positive control band

Successful double freeze/thaw screening method

Conclusion

• Tomato plants from mixed species of hay tended to have more fresh shoot biomass.

• Tomato plants from rye + vetch tended to show less disease symptom, significantly in 1/3fields.

• Double freeze-thaw has been successfully optimized to screen for Mitsuaria and Burkholderia PCR.

12

Future Study

Screen and identify potential bacteria isolates

using a sequence marker following the method

of Benitez et al. (2009).

13

Literature Cited

1) Baysal, F., M. S. Benitez, M. D. Kleinhenz, S. A. Miller, and B. B. McSpadden Gardener.

2008. Field management effects of damping-off and early season vigor of crops in a

transitional organic cropping system. Phytopathology 98:562-570.

2) Benitez, M. S., and B. B. McSpadden Gardener. 2009. Linking Sequences to Function in

Soil Bacteria: Sequence-Directed Isolation of Novel Bacteria Contributing to Soilborne Plant

Disease Suppresion. Appl. Environ. Microbiol. 75:915-924.

3) Pal, K. K., and B. B. McSpadden Gardener. 2006. Biological Control of Plant Pathogen.

The Plant Health Instructor DOI: 10.1094/PHI-A-2006-1117-02.

4) Schonbeck, M., and Morse, R. 2006. Cover Crops for all Seasons: Expanding the cover

crop tool box for organic vegetable producers. Virginia Association for Biological Farming

Information Sheet.

14

Acknowledgements

• Funding to support the development of these materials

was provided by the USDA’s Organic Agriculture

Research and Extension Initiative Grant 2009-51300-

05512.

• Many thanks to Summer Research Opportunity Program

at the Ohio State University

• Special thanks to Chunxue Cao, Xiaoqing Rong,

Veronica Cepeda and Matthew Worth for assisting with

field works.

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McSpadden Gardener’s Lab Members

Summer 2011

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Thank You!