PPath 590 FRIDAY Seminar: Downy mildew diversity and the population structure of Pseudoperonospora cubensis in North Carolina

Emma Wallace
Emma Wallace

Emma Wallace

Date and Location

When (Date/Time)

April 27, 2018, 12:20 PM - 1:20 PM


201 Buckhout Laboratory

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(Practice Seminar on Tuesday April 17, 2:00 PM)

Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew, is an obligate biotrophic pathogen in the Oomycota. This pathogen can cause severe economic losses on all commercial cucurbits produced in the United States (US). It is known that the pathogen spreads up the east coast from Florida via wind dispersal each year, but the role of non-commercial and wild cucurbit hosts has not been considered in the epidemiology of the disease and diversity of the pathogen. Additionally, previous studies demonstrated high genetic diversity of P. cubensis in North Carolina (NC) relative to other regions in the US. Therefore, the authors sought to examine the population structure of P. cubensis in NC based on factors such as location, commercial and non-commercial host, year, and growing season. This was achieved by identifying non-commercial cucurbits hosts for P. cubensis in NC, developing molecular markers to assess populations of P. cubensis, and using the molecular markers to assess populations of P. cubensis across commercial and non-commercial hosts in NC. Three non-commercial cucurbits were shown to become infected with P. cubensis in a field setting, and Koch’s postulates were conducted to confirm the disease. Next, eleven informative microsatellite markers were identified using in silico techniques and laboratory screening. Finally, samples were genotyped with the identified microsatellite markers and population genetics analyses were conducted. Results demonstrated that a majority of the samples grouped into one of two distinct genetic clusters. A majority of P. cubensis isolates that grouped in Cluster 1 were from Cucumis hosts and a majority of the isolates that grouped in Cluster 2 were from Cucurbita hosts. Samples from non-commercial hosts grouped in both genetic clusters. Overall, our study shows that host plays an important role in shaping P. cubensis populations.