Botrytis pseudocinerea, a new cryptic species causing gray mold in French vineyards in sympatry with Botrytis cinerea.

Botrytis cinerea is a major crop pathogen infesting >220 hosts worldwide. A cryptic species has been identified in some French populations but the new species, B. pseudocinerea, has not been fully delimited and established. The aim of this study was to distinguish between the two species, using phylogenetic, biological, morphological, and ecological criteria. Multiple gene genealogies confirmed that the two species belonged to different, well-supported phylogenetic clades. None of the morphological criteria tested (spore size, germination rate, or mycelial growth) was able to discriminate between these two species. Sexual crosses between individuals from the same species and different species were carried out. Only crosses between individuals from the same species were successful. Moreover, population genetics analysis revealed a high level of diversity within each species and a lack of gene flow between them. Finally, a population survey over time showed that B. cinerea was the predominant species but that B. pseudocinerea was more abundant in spring, on floral debris. This observation could not be explained by temperature adaptation in tests carried out in vitro or by aggressiveness on tomato or bean leaves. This study clearly establishes that B. cinerea and B. pseudocinerea constitute a complex of two cryptic species living in sympatry on several hosts, including grapevine and blackberry. We propose several biological or molecular tools for unambiguous differentiation between the two species. B. pseudocinerea probably makes a negligible contribution to gray mold epidemics on grapevine. This new species has been deposited in the MycoBank international database.