Distribution of benzimidazole-resistant strains of the onion gray-mold neck rot pathogens, Botrytis aclada and Botrytis allii, in Hokkaido, Japan

Botrytis aclada and Botrytis allii , associated with onion gray-mold neck rot and isolated in Hokkaido, were tested for sensitivity to benzimidazole. Of the B . aclada strains, 59% were highly resistant and the remaining 41% were sensitive; all strains of B . allii were sensitive. Resistant strains were widespread in Hokkaido. We analyzed the sequences of the β-tubulin gene of resistant strains and detected the replacement of glutamic acid (GAG) by lysine (AAG) at codon 198. This is the first report of benzimidazole resistance in B. aclada . This study revealed a difference in fungicide sensitivity between the two Botrytis species.