Wheat sharp eyespot, caused by the soilborne basidiomycete fungus Rhizoctonia cerealis group D subgroup I (AG‐DI), is a common disease of wheat stems that has increased in global importance in recent years. The disease caused a severe and extensive epidemic throughout the Willamette Valley of Oregon in 2014 and has remained one of the most important wheat diseases in this region subsequently. The population structure of this pathogen is still not well understood. In this study, 572 pure cultures of R. cerealis AG‐DI were isolated from five commercial fields and two experimental fields in the Willamette Valley, Oregon, in the spring of 2017 and 2018. Population structure studies were conducted using six microsatellite markers. Polymorphisms were observed at all six loci, and all seven subpopulations showed moderate gene and genotype diversity. Most of the loci were in Hardy–Weinberg equilibrium in the subpopulations, the entire population combined over locations and five of seven subpopulations were in gametic equilibrium, and the AMOVA and Mantel’s test demonstrated no differentiation among subpopulations. Though direct evidence is currently lacking, these results suggest that the sexual stage of the pathogen may be having a significant impact on pathogen population structure, and that the presence of basidiospores could be contributing to the extensive spread of this disease in the Willamette Valley in recent years.

中文翻译：

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美国俄勒冈州威拉米特河谷小麦尖眼病原体麦草根瘤菌的遗传结构和种群多样性

小麦纹枯病，造成土壤传播的担子菌类真菌纹枯病组d亚组I（AG-DI），是小麦的常见病茎已经在全球的重要性在最近几年有所增加。该病在2014年导致了俄勒冈州威拉米特山谷的严重而广泛的流行病，随后一直是该地区最重要的小麦病之一。这种病原体的种群结构仍不十分清楚。在这项研究中，有572种纯净的R. AG‐DI were isolated from five commercial fields and two experimental fields in the Willamette Valley, Oregon, in the spring of 2017 and 2018. Population structure studies were conducted using six microsatellite markers. Polymorphisms were observed at all six loci, and all seven subpopulations showed moderate gene and genotype diversity. Most of the loci were in Hardy–Weinberg equilibrium in the subpopulations, the entire population combined over locations and five of seven subpopulations were in gametic equilibrium, and the AMOVA and Mantel’s test demonstrated no differentiation among subpopulations. Though direct evidence is currently lacking, these results suggest that the sexual stage of the pathogen may be having a significant impact on pathogen population structure, and that the presence of basidiospores could be contributing to the extensive spread of this disease in the Willamette Valley in recent years.