First report of peach powdery mildew caused by Podosphaera leucotricha in Japan

Abstract

Brown spot of peach fruit was found in Nagano Prefecture, Japan, the causal agent identified and disease development revealed. Hyphae were observed on the surface of brown spot lesions using SEM, but conidia were not found, and rDNA ITS sequence of extracted DNA had 100% identity to that of Podosphaera leucotricha. Inoculation with P. leucotricha caused the brown spot on young peach fruit, and DNA of P. leucotricha was re-extracted from the lesion. Therefore, P. leucotricha causes peach brown spot in addition to peach rusty spot reported in Serbia. The symptom looks like peach powdery mildew caused by P. pannosa, but conidia were absent; hence, it should be included among peach powdery mildews. Podosphaera leucotricha infected fruit between 0 and 20 days after petal fall, and symptoms appeared about 15–40 days after infection. Brown spot was observed in peach orchards 15 days after petal fall, and rates of peach fruit with brown spot was increased rapidly about 3 weeks. Because conidia were not found on peach, powdery mildew on apple tree is a likely infection source for peach brown spot.