Collapsimycopappus: A new leaf pathogen with mycopappus‐like propagules in Mycosphaerellaceae

Abstract

A previously undescribed mycopappus‐like fungus associated with large zonate leaf spot disease of Styrax obassia was found in Japan. Single‐propagule isolation of the fungus from necrotic areas of the diseased leaves yielded four pure cultures. Pathogenicity tests of the fungus were performed on potted S. obassia plants. Leaves were wounded with a sterilized needle and inoculated with mycelial agar. Development of necrotic zones was observed within 4 months. Numerous propagules appeared on the necrotic areas, and two strains of the same fungus were isolated again. The morphology of the pathogen was described, and its phylogeny was analysed based on the sequences of nuclear rDNA ITS, LSU regions and the rpb2 genes. Twenty‐four sequences were generated from six strains. Phylogenetic analyses indicated that the pathogen was closely related to the members of Mycosphaerellaceae, but was distinct in having brown propagules with hyphal appendages that collapsed at maturity and divided into part spores. Therefore, we propose Collapsimycopappus as a new genus to accommodate a single species, C. styracis.