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Oral: Pathogen Ecology


Ecological Impact of Signaling Chemicals on Phytophthora erythroseptica
H. JIANG (1), J. Hao (1) (1) University of Maine, U.S.A.

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Phytophthora erythroseptica causes pink rot of potato, mostly with zoospores as major primary inocula. Zoosporic germination and infection of host (potato) are regulated by signaling molecules with quorum sensing mechanism. This study was to determine if the signals were species specific and if they were impacted by the environment. Exudates were obtained from high concentrations of fungi, bacteria, and oomycetes, as well as soil and roots of potato varieties. The exudates were used to treat zoospores of P. erythroseptica. Results showed that several soil microorganisms, including P. capsici, P. cactorum, Pythium irregulare, Serratia sp., Delftia sp., and Microbacterium sp. induced zoosporic germination of P. erythroseptica; Pseudomonas spp. and Bacillus amyloliquefaciens inhibited zoosporic germination; exudates of Dickeya dadantii and Pectobacterium carotovorum had no effect on zoosporic germination. Root exudate from the pink-rot-sensitive variety, ‘Dark Red Norland,’ induced zoosporic germination, while tolerant variety ‘Snowden’ did not. These results indicate that the zoosporic behavior is not only self-regulated, but also affected by other environmental organisms, such as host plants and soil microorganisms through signaling molecules. Whether same signals are shared among organisms is being investigated. This result may improve our understanding of the initiation and development of potato pink rot and contribute to breeding resistant potato cultivars.