Genetic Dynamics and Mating Type Inheritance in an Experimental, Overwintering Biparental Population of Phytophthora capsici
M. CARLSON (1), E. Gazave (2), M. Gore (2), C. Smart (1) (1) Cornell University, Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, U.S.A.; (2) Cornell University, Plant Breeding and Genetics Section, School of Integrative Plant Science, U.S.A.

The common co-occurrence of both A1 and A2 mating types of Phytophthora capsici results in production of oospores, and consequently persistent, overwintering populations in many locations. To understand the dynamics of these often isolated, sexual populations, a restricted access research farm in Geneva, NY, with no prior history of P. capsici, was inoculated in 2008 with two isolates of opposite mating type. Approximately 50 isolates were sampled each year, from 2009-13, from a variety of plant species. To provide a controlled reference for the field study, F1 single-oospore progeny were collected from an in vitro cross between the same founding parents. Isolates were analyzed using genotyping-by-sequencing (GBS), which simultaneously identifies and scores single nucleotide polymorphism (SNP) markers, resulting in approximately 25,000 genome-wide SNP markers. Indicators of inbreeding, multi-locus heterozygosity and the inbreeding coefficient, show that over time the population underwent a generational shift; transitioning from putative F1 in 2009-10, to mixed generational in 2011, and ultimately all inbred in 2012-13. In addition, limited observation of putative selfed isolates in the field suggests that selfing contributes minimally to field population structure. Capitalizing on the segregation of mating type (MT) in this population, we performed a genome-wide association study to identify loci associated with MT. Our results support a hypothesis for four segregating haplotypes in the MT region, potentially defined by structural variation. Genome sequencing of the A1 founding parent and analysis of segregation in this region will provide insight into the genetic structure of the MT region.

Abstract Number: P13-410
Session Type: Poster