APS Homepage

TECHNICAL SESSION: Elucidation of plant immune responses to bacterial plant pathogens

Recent advances to control soft rot disease
Janak Joshi - Colorado State University. Iris Yedidia- Agriculture Research Organization, Adam Heuberger- Colorado State University, Amy Charkowski- Colorado State University

Pectobacterium sp. are devastating pathogen of potato and ornamentals and there are limited options for management of this pathogen. Ornamental Ornithogalum lines were transformed with the antimicrobial peptide tachyplesin I to obtain soft rot resistance plants and transformant resistance was correlated with tachyplesin I level in transformed plant lines. Furthermore, to identify traits associated with resistance to Pectobacterium, sensitive and resistant lines of the Ornithogalum were crossed, and Pectobacterium-resistant offspring were selected. Resistance levels of the parental and progeny lines were correlated with the level of phenolic content in the plant lines. In addition, plant phenolic molecules were screened for antimicrobial activity and the best performing phenolics, salicylic acid and carvacrol, were studied to understand their mode of action. These two molecules affected the bacterial quorum sensing system, resulting in low synthesis of exoenzymes, thereby reducing virulence. Collectively, these discoveries suggest that plant phenolics are a useful breeding target to develop Pectobacterium-resistant plant varieties and that plant phenolics can promote resistance by interfering with regulation of bacterial virulence genes.