Identification and characterization of Botrytis medusae, a novel cryptic species causing grey mould on wine grapes in Australia

Abstract

In a collection of 735 Botrytis isolates sampled from Australian wine grape-growing regions, a single isolate from clade I and group I (based on Bc-hch RFLP analysis) was found. As many Botrytis species are known to live sympatrically, it was hypothesized that this isolate might be a new Botrytis species. After phenotypic and molecular assays supported this hypothesis, the species was designated B. medusae. Phylogenetic analyses using the nuclear genes G3PDH, HSP60, RPB2, NEP1 and NEP2 consistently placed B. medusae in an early-diverging clade I Botrytis spp. lineage. Botrytis medusae produced white aerial mycelium, grew faster at 30 °C and produced long-branched conidiophore extensions, compared with B. cinerea and B. pseudocinerea. Botrytis medusae was only able to infect wounded grape leaves and was significantly less virulent on wounded leaves and berries than B. cinerea. Botrytis medusae also lacked villiform appendages on the conidial surface and long conidiophores, which are defining features of B. sinoviticola and B. californica, respectively. Identification and characterization of new cryptic Botrytis species living in sympatry on grapevines could potentially provide information to assist disease management strategies for B. cinerea.