Pseudocercospora fengxinensis, a New Species Causing Sooty Spot of Kiwifruit in China.

Pseudocercospora is a large cosmopolitan genus of plant pathogenic fungi that are commonly associated with leaf and fruit spots as well as blights on a wide range of plant hosts. P. actinidiae is a member of this genus, causing sooty spot on kiwifruit worldwide. With the expansion of kiwifruit cultivation, the incidence of sooty spot has become severe in Fengxin County, Jiangxi Province, China. Based on a survey conducted in 2022 across nine kiwifruit cultivars in six local orchards, the results showed that the disease incidence was higher in 'Donghong', 'Jinyan', 'Jinkui', 'Fenghuang No. 1', and 'Jinguo'. In contrast, it was lower in 'Gold3' and 'Hongshi No. 2'. No lesions were observed on 'Kuilv' and 'Miliang No. 1'. Thirty-one fungal strains were isolated from infected leaves using single-spore isolation. Phylogenetic analysis of combined sequence data from the internal transcribed spacer region of ribosomal DNA (ITS), partial actin (actA), translation elongation factor 1-alpha (tef1), and the second largest subunit of RNA polymerase II (rpb2) sequence data, using maximum-likelihood and Bayesian inference, revealed their taxonomic placement within Pseudocercospora. Both morphological and molecular phylogenetic analysis supported Pseudocercospora fengxinensis as a new taxon within Pseudocercospora. Pathogenicity tests confirmed P. fengxinensis as the causal agent of sooty spot on kiwifruit. This study is the first report of P. fengxinensis causing sooty spot of kiwifruit worldwide, enriching our understanding of Pseudocercospora diversity in China and providing a foundation for improved disease management strategies.