New races of the spinach downy mildew pathogen, Peronospora farinosa f. sp. spinaciae, in Japan in 2017

摘要

Six isolates of spinach downy mildew fungus, Peronospora farinosa f. sp. spinaciae, collected from Saitama and Ibaraki Prefectures in 2017 were identified. Three isolates collected from Saitama Prefecture in January differed from all the known races described by the International Seed Federation but their virulence was similar to that of strain UA1014 sampled in the USA in 2014. Isolate Iba17-2, collected from Ibaraki Prefecture in April, was identified as race 10; isolates Iba17-1 and Iba17-3, collected from the same region in February and May, did not match any known races and were coded as novel races, J17-1 and J17-2, respectively.