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Population Structure of the oomycete soilborne pathogen Phytophthora capsici in North Carolina
Camilo Parada Rojas: North Carolina State University; Lina Quesada: North Carolina State University
<div><i>Phytophthora capsici</i> is a devastating oomycete plant pathogen that affects solanaceous, cucurbitaceous, fabaceous, and other crops in the United States (US) and worldwide. Previous studies have documented high genetic variation in US populations and geographic stratification since <i>P. capsici</i> has limited dispersal resulting in isolated field populations. Despite its impact in vegetable production, <i>P. capsici</i> population structure in North Carolina (NC) is unknown. In this study, more than 120 isolates of <i>P. capsici</i> collected from different regions of NC were assayed for mefenoxam, fluopicolide, dimethomorph, and oxathiapiprolin resistance and genotyped using eleven microsatellite loci and fragment analysis. Preliminary data suggest that fungicide resistance is more common in some NC counties than others. Both mating types A1 and A2 are present across NC, but A2 <i>P. capsici</i> isolates are the most common throughout the state. Population analyses revealed that the greatest genetic differentiation occurs when isolates are grouped by location more so than when grouped by host, mating type, or fungicide sensitivity. Our results indicate that <i>P. capsici</i> is highly diverse in NC, but isolate genotypes remain structured by location; therefore, deployment of fungicides and resistant cultivars must account for spatial distribution of genetic and phenotypic diversity.</div>

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