Drunken horse grass (Achnatherum inebrians) plays a vital role in ecological restoration and grassland sustainability in Northwest China, but its ecological functions are increasingly threatened by emerging fungal diseases. In 2024, a leaf spot disease characterized by brown lesions with yellow halos was observed on drunken horse grass in Gansu Province, China. The causal pathogens were identified as Alternaria alternata and Alternaria infectoria based on morphological characterization, pathogenicity tests, and multi-locus phylogenetic analysis (ITS, TEF, GPD, RPB2, Alt a 1, endoPG, and OPA10-2). Preliminary fungicide sensitivity assays revealed that tetramycin and difenoconazole had the strongest inhibitory effects against mycelial growth in vitro. The EC50 values for tetramycin were 0.0755 mg/L (A. alternata) and 0.2175 mg/L (A. infectoria), while for difenoconazole, they were 0.1023 mg/L (A. alternata) and 0.0599 mg/L (A. infectoria). To our knowledge, this is the first report of Alternaria species infecting the host plant, drunken horse grass, providing an essential basis for the effective management of this disease and the protection of grassland ecosystems.
Liang et al. (Fri,) studied this question.