First report of Alternaria alternata causing black spot disease on Salvia miltiorrhiza in China

Salvia miltiorrhiza is a perennial herb of the Lamiaceae family and an important traditional Chinese medicinal plant. Nanyang in Henan Province is its principal production area, where disease problems have become increasingly prominent under large-scale cultivation. In June 2025, a leaf black spot disease was observed in S . miltiorrhiza plantations in Nanyang. The disease mainly affected leaves and, in severe cases, caused defoliation and branch dieback. In this study, the pathogen was isolated using a tissue isolation method, and a systematic investigation was conducted through morphological observation, multi-gene molecular identification, and pathogenicity assays. Morphological results showed that the colony, mycelial, and conidial characteristics of the isolates were consistent with those of the genus Alternaria . Sequence comparison and phylogenetic analyses based on the ITS, tef1 , and Alt a 1 genes indicated that the isolates shared 99–100% similarity with Alternaria alternata . Pathogenicity was verified according to Koch's postulates. This study is the first to confirm that A . alternata is the causal agent of black spot disease of S . miltiorrhiza in the Nanyang region of China, providing a scientific basis for precise disease management.