Phylogenetic reassessment and epitypification of Exobasidium vexans causing blister blight of tea

Exobasidium vexans is an important tropical phytopathogenic fungus that causes blister blight in tea. Despite its devastating impact on tea cultivation, this pathogen remains poorly studied. In this study, fresh symptomatic leaf samples of blister blight were collected from the main tea-growing regions of Sri Lanka and from Northeast and Eastern India, where the disease was originally reported. Fresh collections obtained from each locality were characterized based on micromorphological characters and molecular data and an epitype was designated. A molecular phylogeny based on the ITS (ribosomal nuclear internal transcribed spacer 1, 5.8S, internal transcribed spacer 2), 28S rDNA (largest subunit of ribosomal gene partial sequence), and TEF-1α (translation elongation factor-1 alpha) revealed that E. vexans collections represent a monophyletic clade closely related to E. reticulatum. This study provides crucial insights into the phylogenetic position and genetic diversity of E. vexans, offering a foundation for future studies on its biology, epidemiology, and management to mitigate impact on global tea production.