Biological control of Pierce’s disease: Influence of grape genotype, plant growth stage, and geographic location

D. L. Hopkins Mid-Florida RECUniversity of Florida

Phil BrannenPlant Pathology Dept.University of Georgia

Biological Control of PD with strain EB92-1

• Grape Genotypes

• Mature, Producing Grapevine

• Different Geographic Areas

• Treatment Methodology

• Colonization

Current tests on new grape plantings of various grape genotypes

Field injections

Greenhouse injection

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Cab.Franc Chamb. Cynth.

Grape Genotypes

Untreated

EB92-1

• Effect of strain EB92-1 on PD in various genotypes, V. vinifera (Cabernet Franc), V. aestivalis (Cynthiana), and French/American hybrid (Chambourcin) in the vineyard in Central Florida.

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Chardon. CheninBlanc

GoldenMuscat

RubyCabernet

Grape Genotypes

Untreated

EB92-1

Effect of strain EB92-1 on PD in various cultivars in Central Florida

Additional Genotype Studies

• North Carolina – Mature plants of Vitis labrusca cultivars Canadice, Concord Seedless, Einset, Glenora, Himrod, Interlaken, Jupiter, Lakemont, Marquis, Mars, Reliance, Suffolk Red, Vanessa, and Venus.

• South Carolina – Young transplants of Vitis labrusca cultivars Jupiter, Neptune, Mars, and Venus.

• Georgia – Young transplants of Cabernet Sauvignon, Cabernet Franc, and Vidal Blanc (hybrid).

• California – Young transplants of Cabernet Sauvignon, Orange Muscat, Barbera, Viognier, Reisling, and Chardonnay.

Inoculated approximately 107 cells EB92-1 per plant into 2nd and 3rd internodes.

Mature Plant Treatments

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2006 2007 2008

Year

Untreated

EB92-1

Effect of EB92-1 on development of PD in mature ‘Mourvedre’ grapevines in North Georgia vineyard with a high incidence of PD

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2006 2007 2008

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Untreated

EB92-1

Untreated

EB92-1

Effect of EB92-1 on survival of symptomatic, mature ‘Mourvedre’ grapevines in North Georgia vineyard

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16%

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2006 2007 2008

Year

Untreated

EB92-1

Effect of EB92-1 on development of PD in mature ‘Mourvedre’ grapevines in North Georgia vineyard with a low incidence of PD

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2006 2007 2008

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UntreatedEB92-1

Effect of EB92-1 on survival of symptomatic, mature ‘Mourvedre’ grapevines in a North Georgia vineyard

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Planned Mature Plant Study for 2009

Inject EB92-1 into the main trunk of the vines to get more systemic affect

North Georgia

Central Florida North Carolina

South Carolina

Different Locations (Climates)

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Florida Georgia S. Carolina

State

Untreated

EB92-1

Effect of EB92-1 on development of PD in new plantings in Florida (4 years - Cabernet Franc, Chardonnay, Chenin Blanc, Golden Muscat, Ruby Cabernet), Georgia (1 year – Cabernet Sauvignon, Cab. Franc, Vidal Blanc), S. Carolina (1 year – Neptune)

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Chardonnay Chambourcin

Cultivar

RC Untreated

EB92-1 RC

RC injected EB92-1

Comparison of treatment method with EB92-1 on control of Pierce’s disease in rooted cuttings in the greenhouse.

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EB92-1 Treatment Methodology

Effect of EB92-1 on host colonization by the virulent Pierce’s disease strain

• Rooted cuttings of Carignane grapevine with >18 inches of new growth were used.

• Plants were inoculated with a suspension of EB92-1 (108 cells/ml). One drop was inoculated into the 1st and 2nd internodes (total 107 cells/plant).

• Three weeks later, plants were inoculated with a suspension of PD92-9, a virulent PD strain (106 cells/ml). One drop was inoculated into opposite sides of the 3rd internode (105 cells/plant).

• The 3rd internode (0, pathogen-inoculated internode) and the 13th internode were sampled for grinding and dilution plating.

• EB92-1 and PD92-9 were labeled with different colored fluorescent proteins for differentiation on culture plates.

Growth curves of strains in grape stem internode 10

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Weeks after inoculation

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Virulent

Combo Virulent

Comb Biocontrol

105 PD92-9 cells

Colonization of host plant by EB92-1 and pathogen (PD92-9

Growth curves of strains in inoculated grape stem internode (0)

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Weeks after inoculation

Bac

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Virulent

Combo Virulent

Comb Biocontrol

105 PD92-9 cells

Summary

• Grape Genotypes – In Florida, EB92-1 was effective in Vitis vinifera cultivars, V. aestivalis, and American hybrids. Tests are in progress on other cultivars in other locations.

• Mature, Producing Grapevine - Treatment of mature grapevines did not reduce new cases of PD in the first year, but may have had a slight benefit in year 2 and 3. Treated vines that developed PD symptoms had a better survival rate in year 2 and 3 than the untreated.

• Different Geographic Areas – Biological control has been very effective on transplants in Florida. Preliminary data is positive in Georgia and South Carolina.

• Treatment Methodology - Propagating rooted cuttings from mother vines infected with EB92-1 was inconsistent in biological control of Pierce’s disease, providing control in Chambourcin and not in Chardonnay.

• Colonization - In greenhouse inoculations, EB92-1 prevented the pathogenic Pierce’s disease strain from reaching a threshold population in the plant needed to produce disease.

Thanks!