Multilocus phylogeny, species delimitation, and pathogenicity reveal a novel Botrytis species causing gray mold of Cordyline fruticosa

Severe foliar disease was observed on Cordyline fruticosa in a horticultural nursery in Banan District, Chongqing, China, from May 2025 to February 2026. Symptoms consisted of circular to oval, brown to dark brown lesions with yellow halos that coalesced to cause whole-leaf blight and necrosis. Fungal isolates belonging to the genus Botrytis were recovered from symptomatic leaf tissues. A three-locus dataset comprising partial sequences of RNA polymerase II second largest subunit (RPB2), heat shock protein 60 (HSP60), and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) was generated for these isolates. Phylogenetic analyses using the Genealogical Concordance Phylogenetic Species Recognition (GCPSR) framework identified a previously undescribed Botrytis taxon. Species boundaries were further validated via an integrative polyphasic approach, including phylogenetic network reconstruction, Pairwise Homoplasy Index (PHI) test, Discordance-Based Species Recognition (DBSR), and Concordance-Based Species Recognition (CBSR) analyses of the three-locus dataset. All species delimitation methods yielded congruent results, supporting its recognition as a distinct novel species. Pathogenicity assays confirmed that this novel Botrytis species was the causal agent of the foliar disease on C. fruticosa. Collectively, this study formally describes a novel Botrytis species causing gray mold on C. fruticosa and expands the known host range of the genus Botrytis. The findings provide essential baseline data for the early diagnosis and targeted management of this emerging gray mold disease on ornamental Cordyline plants.