Two species of Stemphylium, S. astragali and S. henanense sp. nov, causing leaf and stem spot disease on Astragalus sinicus L. in China

Astragalus sinicus L. is a versatile legume crop, primarily being utilized as a green manure in China. During 2020-2021, A. sinicus plants exhibiting dark brown or reddish-brown lesions or spots on leaves and stems were collected from the fields in Henan, Sichuan and Guangxi provinces of China. Sixteen single spore isolates were isolated from the infected leaf and stem tissue samples. Phylogenetic analyses based on the concatenated ITS, gapdh and cmdA sequences indicated that fourteen of them belong to Stemphylium astragali while two isolates can be well separated from other known species in this genus. Based on the morphological characteristics and nucleotide polymorphisms with sister taxa, the two isolates were identified as a new species named S. henanense. Furthermore, pathogenicity assays showed that the S. astragali and S. henanense isolates caused leaf and stem spot symptoms on A. sinicus. Altogether, we describe a new species of Stemphylium, i.e., S. henanense sp. nov., causing leaf spot disease of A. sinicus. In addition, this is the first report of S. astragali causing stem spot disease of A. sinicus.