Pathogenicity and taxonomy of Tenuignomonia styracis gen. et sp. nov., a new monotypic genus of Gnomoniaceae on Styrax obassia in Japan

Abstract Since 2010, an unknown fungusin the Gnomoniaceaehas been found on overwinteredleaves and petioles of Styrax obassia( Styracaceae) in Japan. This fungusis characterized by dark brown immersed or partially erumpent ascomata with long necks and fusiform to obovoid asci each with an acute or long tapering stipe. Each ascusbears eight fusiform to filiform ascospores. Our morphological observation and phylogenetic analyses based on the markers LSU, rpb2 , and tef-1α indicated that this is a new monotypic genus in the Gnomoniaceae( Diaporthales), and Tenuignomonia styracis gen. et sp. nov. was descried herein. Members of the Gnomoniaceaeare commonly isolated as endophytes, saprobes, and plant pathogens from a broad diversity of herbaceous, shade tree, and agriculturally significant plants. We thus carried out a pathogenicity test to determine if T. styracis is the causative agent of leaf blotch on S . obassia . One week after inoculation, this fungusproduced small necrotic spots on the leaves and petioles, and all leaves having necrotic spots were abscised in a short time. We thus confirmed that this fungushas weak pathogenicity on S . obassia . This new species may promote early defoliationof S . obassia during the fall.