Measuring Single Nucleotide Polymorphism in the Vegetable Pathogen <i>Phytophthora capsici</i>

Phytophthora capsici is a eukaryotic plant pathogen that causes root, fruit, and foliar disease on a variety of important vegetables including pepper, tomato, eggplant, snap and lima beans, and essentially all cucurbits. At some locations, populations utilize sexual and asexual reproduction, whereas at others, populations appear to be entirely asexual. The differing population structure has important implications for developing control strategies. Our objective was to develop SNP markers to characterize natural populations and laboratory crosses. In chapter two, a novel technique to assay SNP genotypes based on high-resolution DNA melting analysis is presented. In chapter three, the genetic diversity for P. capsici isolates collected at diverse locations in Argentina is summarized. Clonal reproduction dominated over a wide geographical area and multiple years. The genetic diversity for P. capsici isolates collected on Long Island, New York, USA is summarized in chapter four, suggesting that both sexual and clonal reproduction play important roles in the epidemiology. And lastly, the genetic diversity of P. capsici isolates collected from peppers grown in France is discussed in chapter five. The results from France are similar to the USA and it appears that both sexual and asexual reproduction play an important role in the epidemiology.