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

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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.

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Intro (cont.)

Cover Crop

Planting time

Mature time

Benefits

Radish Early Spring

Late summer

NR= take up and holds soluble soil nitrogenB= harbors beneficial insectsTS= conditions, mellow top soil

Winter Rye

Fall May NR= takes up and holds soluble soil nitrogenK= makes soil potassium more available

Hairy Vetch

Early fall May N= fixed nitrogenB= harbor beneficial insectsP= make soil phosphorous more available

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Schonbeck and Morse (2006)

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

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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.

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Methods

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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 biomassabove 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

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Fig. 1: % Organic Matter

Results_ Soil fertility

No significant difference of cover crops on % organic matter

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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

FryAFr

y

East Bad

ger

Vetc

h

Rye Ve

tch

Rye

Radish

Mixed

hay

Vetch

Rye Ve

tch

Rye

Radish

Mixed

hay

Vetch

Rye Ve

tch

Rye

Radish

Mixed

hay

1800

1600

1400

1200

1000

800

600

400

200

Fresh

shoot

bio

mass

, g

9Plants from mixed hay soil have more fresh shoot weight

Results_ % disease symptoms

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Fig. 4: Ranking score of percentage disease symptoms Less disease symptom plants from rye + vetch soil,significantly 1/3 fields

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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 bandSuccessful 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.

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Future Study

Screen and identify potential bacteria isolates using a sequence marker following the method of Benitez et al. (2009).

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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.

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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!