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Oral: Population Dynamics


Pseudoperonospora cubensis on commercial and non-commercial cucurbits in North Carolina: population structure determined by simple sequence repeats
E. WALLACE (1), L. Quesada-Ocampo (2) (1) NCSU, U.S.A.; (2) NCSU, U.S.A.

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The cucurbit downy mildew pathogen, Pseudoperonospora cubensis, is a major limiting factor in cucumber production in the United States (US). Each year, P. cubensis causes foliar destruction on cucumber, but it also infects approximately 60 host species in the Cucurbitaceae family. All major commercial cucurbits are hosts in the US. Many non-commercial hosts are grown on a small scale or occur as weeds and their contributions to the yearly P. cubensis epidemic are understudied. North Carolina (NC) has diverse cucurbit production and previous studies have found that NC has relatively high genetic diversity of P. cubensis. In this study, Simple Sequence Repeats (SSRs) were identified in silico from the P. cubensis predicted transcriptome. A subset of the identified markers were screened and evaluated for reliability and polymorphism. Eleven markers were selected and applied to P. cubensis isolates collected from six commercial and three non-commercial cucurbits across four time points and three regions in NC. Population analyses revealed that the greatest genetic differentiation occurs when isolates are grouped by host species more so than when grouped by location or time. These findings show host species are playing the most significant role in P. cubensis diversification in NC. The results suggest non-commercial cucurbits could be contributing to P. cubensis inoculum for certain hosts more so than others, thus influencing the population dynamics of the pathogen.