A New Leaf Spot Disease Caused by <i>Alternaria jacinthicola</i> on <i>Durio zibethinus</i> in China

ABSTRACT A leaf spot disease with an incidence of approximately 50% and a severity rate of around 70% was found on Durian in Hainan Province, China, in July 2023. The early symptoms appeared as light grey to dark brown, irregular, small, necrotic lesions, distributed along the leaf veins. As the disease progresses, the lesions turned to rusty‐coloured necrotic spots and pale yellow chlorotic halos or rings around the edges, even extensive leaf death and defoliation, severely impairing photosynthesis. Alternaria jacinthicola and Alternaria tomato were isolated from diseased durian leaves, and only A. jacinthicola was identified as the predominant pathogen through morphological and multi‐gene phylogenetic analysis. Pathogenicity assays demonstrated its ability to infect both durian leaves and fruits. To our knowledge, this is the first report of A. jacinthicola causing leaf spot disease on durian. These findings lay the foundation for further research into the pathogenesis of durian diseases and the development of effective control measures.