Geographic Distribution and Genetic Diversity of Three Ophiosphaerella Species that Cause Spring Dead Spot of Bermudagrass.

The distribution of three Ophiosphaerella spp. that cause spring dead spot (SDS) of bermudagrass was studied by systematically sampling two golf courses in Oklahoma and one in Kansas. O. herpotricha was isolated from all three locations and was the most abundant species. It was the only SDS pathogen found at Jenks, Oklahoma. O. korrae was isolated from Afton, Oklahoma, and Independence, Kansas, whereas O. narmari was only detected in samples from Afton. This is the first report of all three Ophiosphaerella species on bermudagrass at the same location. Amplified fragment length polymorphism (AFLP) marker analysis was used to investigate inter- and intraspecific genetic diversity of Ophiosphaerella isolates from North America and Australia. A majority of the O. herpotricha and O. narmari isolates from Afton were distinct haplotypes, suggesting that sexual recombination was occurring within the population. Conversely, the presence of multiple isolates of O. herpotricha and O. narmari with the same haplotype also indicated that asexual propagation was occurring. The genetic diversity among O. herpotricha isolates from Afton was not distinctly different from that of isolates collected throughout the southern United States. In contrast, O. narmari isolates from Afton were distinct from those collected in Australia. The genetic diversity in O. korrae was markedly different than that in the other Ophiosphaerella spp. The population at Afton was dominated by just a few haplotypes, and these were nearly identical to isolates collected from bermudagrass and Kentucky bluegrass throughout western, central, and northern North America. However, O. korrae isolates collected in the southeastern United States were only distantly similar to other North American isolates.