Botrytis cinerea is a filamentous ascomycete fungus which is responsible for gray mold disease. In recent studies, autophagy has been shown to be required for various stages of the life cycle of fungi. In this study, we aimed to investigate the role of autophagy in biologically and agriculturally significant stages of B. cinerea, conidiation, sclerotial development and plant infection. We identified and disrupted the BcATG1 gene, an ortholog of the yeast autophagy gene ATG1. Disruption of BcATG1 caused sensitivity to nitrogen starvation. In addition, the disruptants showed defects in aerial-hyphal growth, consistent with autophagy-deficient mutants in other filamentous fungal species. These results suggested that BcATG1 is required for the function of autophagy in the fungus. Delta BcATG1 strains also indicated reduction in both two types of conidiation. Especially, the disruptants showed severely impaired macroconidiophore development and resulting drastic reduction in macroconidial production. Under cold conditions, sclerotial development was also affected in the disruptants. In pathogenicity tests, Delta BcATG1 strains formed typical disease symptoms on the host plant. Our results suggested that BcATG1 is required for two types of conidiation and sclerotial development, but not for pathogenicity in B. cinerea. (C) 2015 The Mycological Society of Japan. Published by Elsevier B.V. All rights reserved.