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Induction of Plant Defense Gene Expression by Plant Activators and Pseudomonas syringae pv. tomato in Greenhouse-Grown Tomatoes

November 2008 , Volume 98 , Number  11
Pages  1,226 - 1,232

M. A. B. Herman, J. K. Davidson, and C. D. Smart

First and third authors: Department of Plant Pathology and Plant-Microbe Biology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456; and second author: Department of Biology, Hobart and William Smith Colleges, Geneva, NY 14456.

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Accepted for publication 23 July 2008.

Plant activators provide an appealing management option for bacterial diseases of greenhouse-grown tomatoes. Two types of plant activators, one that induces systemic acquired resistance (SAR) and a second that activates induced systemic resistance (ISR), were evaluated for control of Pseudomonas syringae pv. tomato and effect on plant defense gene activation. Benzothiadiazole (BTH, SAR-inducing compound) effectively reduced bacterial speck incidence and severity, both alone and in combination with the ISR-inducing product. Application of BTH also led to elevated activation of salicylic acid and ethylene-mediated responses, based on real-time polymerase chain reaction analysis of marker gene expression levels. In contrast, the ISR-inducing product (made up of plant growth-promoting rhizobacteria) inconsistently modified defense gene expression and did not provide disease control to the same level as did BTH. No antagonism was observed by combining the two activators as control of bacterial speck was similar to or better than BTH alone.

Additional keywords:Bacillus spp., induced defense responses, Solanum lycopersicum.

© 2008 The American Phytopathological Society