Lasiodiplodia carlesii sp. nov. (Botryosphaeriales, Botryosphaeriaceae), a novel pathogen causing canker and dieback on Castanopsis (Fagaceae) plantations in China

Castanopsis , the dominant genus in evergreen broadleaved forests, is widely distributed across South and Southeast Asia. It has significant ecological and economic value, providing resources such as timber, firewood, food, and traditional medicines. China is a center of Castanopsis diversity, with its plantation areas having increased steadily in recent decades. However, severe outbreaks of canker and dieback disease were observed in Castanopsis carlesii and C. hystrix plantations in 2021. In this study, we isolated fungal pathogens from diseased tissues, and identified a novel species, Lasiodiplodia carlesii , based on morphological characteristics and multi-locus phylogenetic analyses of ITS, tef1-α , tub2 , and rpb2 . Pathogenicity tests demonstrated that L. carlesii not only causes canker and dieback symptoms on multiple Castanopsis species (including C. carlesii , C. hystrix , and C. faberi ), but also produces water-soaked brown lesions on the fruits of Syzygium samarangense . These results suggest that L. carlesii has a broad host range, and exhibits cross-family infection. Collectively, this study identifies L. carlesii as a novel pathogen posing a substantial threat to Castanopsis plantations and provides a critical foundation for developing targeted management strategies.