New races of the spinach downy mildew pathogen, Peronospora farinosa f. sp. spinaciae, isolated in Fukuoka Prefecture, Japan in 2019

Abstract

Five isolates of the pathogen that causes downy mildew in spinach, Peronospora farinosa f. sp. spinaciae, collected in Fukuoka Prefecture, Japan, in 2019 were identified as two races, which were distinct from races 1–17 authorized by the International Working Group on Peronospora. The races were temporarily named J19-1 and J19-2. J19-1 reacted to race-differential cultivars similar to an isolate from the United States, UA201502. However, the response of J19-2 to race-differential cultivars differed from any reported races.