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The Snf1 kinase of the glucose signaling pathway controls the response to nutritional and environmental stresses. In phytopathogenic fungi, Snf1 acts as a global activator of plant cell wall degrading enzymes that are major virulence factors for plant colonization. To characterize its role in the virulence of the necrotrophic fungus <i>Botrytis cinerea</i>, two independent deletion mutants of the <i>Bcsnf1</i> gene were obtained and analyzed. Virulence of the Δ<i>snf1</i> mutants was reduced by 59% on a host with acidic pH (apple fruit) and up to 89% on hosts with neutral pH (cucumber cotyledon and French bean leaf). In vitro, Δ<i>snf1</i> mutants grew slower than the wild type strain at both pH 5 and 7, with a reduction of 20–80% in simple sugars, polysaccharides, and lipidic carbon sources, and these defects were amplified at pH 7. A two-fold reduction in secretion of xylanase activities was observed consequently to the <i>Bcsnf1</i> gene deletion. Moreover, Δ<i>snf1</i> mutants were altered in their ability to control ambient pH. Finally, Δ<i>snf1</i> mutants were impaired in asexual sporulation and did not produce macroconidia. These results confirm the importance of <i>BcSnf1</i> in pathogenicity, nutrition, and conidiation, and suggest a role in pH regulation for this global regulator in filamentous fungi.