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POSTERS: Population biology and genetics

Population structure of Globisporangium cryptoirregulare from Rhododendron Nurseries in Oregon
Viviana Freire-Zapata - Oklahoma State University. Yaneth Muñoz- Universidad Francisco de Paula Santander, Cassidy Ward- Oklahoma State University, Carla Garzon- Oklahoma State University, Carolyn Scagel- USDA ARS, Jerry Weiland- USDA ARS, Maria Proano- Oklahoma State University, Niklaus Grunwald- USDA AR

Globisporangium cryptoirregulare (syn. Pythium cryptoirregulare), is the causal agent of root rot and damping-off of a broad range of ornamental crops. Although, root rot disease in Rhododendron is often caused by Phytophthora species, studies performed in Oregon nurseries have found that G. cryptoirregulare is a prevalent pathogen in symptomatic rhododendron roots, causing mild levels of disease. The objective of this study was to assess the diversity and population structure of G. cryptoirregulare isolated from rhododendron in five Oregon nurseries over 4 years, to better understand the population dynamics of this pathogen. A total of 137 samples of G. cryptoirregulare were isolated from rhododendron roots from different nurseries between 2013 and 2016. Samples were analyzed using eight microsatellite loci. Forty-one multilocus (MLG) genotypes were observed. Two clonal genotypes were prevalent in all the nurseries studied. MLG 17 was prevalent from 2013 to 2016 (57 isolates), while MLG 9 was the most common in 2016 only (22 isolates). Low to moderate genetic differentiation was observed between nurseries. Our results suggest low diversity and a high likelihood of gene flow between the five nurseries, with a high likelihood of clonal lineages getting established locally once introduced. Nonetheless, new genotypes were introduced every year, and a new clonal population displaced the previously predominant clone in 2016 in three of the nurseries.