Two Species of Stemphylium, S. astragali and S. henanense sp. nov., Causing Leaf and Stem Spot Disease on Astragalus sinicus in China.

ABSTRACT

Astragalus sinicus is a versatile legume crop, primarily utilized as a green manure in China. During 2020 and 2021, A. sinicus plants exhibiting dark brown or reddish-brown lesions or spots on leaves and stems were collected from fields in the 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 internal transcribed spacer, gapdh, and cmdA sequences indicated that 14 of them belong to Stemphylium astragali, whereas 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.