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Poster: Epidemiology: Population Biology Genetics


Population structure of Pseudoperonospora cubensis isolates in Michigan and Ontario, Canada
J. BELLO (1), Y. Guo (1), M. Hausbeck (1) (1) Michigan State University, U.S.A.

Pseudoperonospora cubensis is a highly destructive obligate oomycete pathogen that incites downy mildew disease in cucurbits worldwide. The pathogen populations in Michigan and Ontario are primarily affected by the movement of sporangia annually from the southern U.S. and Mexico or northern greenhouses where the pathogen can overwinter. The objective of our research was to monitor the population structure change over time in Michigan and Ontario, Canada. Sporangia were collected from cucurbit downy mildew (CMD) lesions using leaves of field grown cucurbits from 2007 to 2010, and sporangia collected in 2015. Population structure and genetic diversity were characterized using three marker types: (1) Selected genomic regions from three mitochondrial and nine nuclear genes previously used in oomycete genetic diversity and phylogenetic studies; (2) Selection from 942 simple sequencing repeat (SSR) markers derived from P. cubensis reference genome that were inside or partially overlapping with the annotated transcripts; (3) Genomic regions containing higher frequency of host and/or species specific single nucleotide polymorphisms (SNPs) adapted from previous studies. This research provides insight into changes of CMD populations in Michigan and Ontario over time which may contribute to overall management strategies.