Identification of Alternaria tenuissima causing brown leaf spot on Paris polyphylla var. chinensis in China

Severe brown leaf spot disease was observed on Paris polyphylla var. chinensis in Sichuan Province, China, in 2017 and 2018. The initial symptoms were many light-brown small spots with necrotic centres, round or irregular in shape, becoming dark brown, gradually enlarging and eventually coalescing, causing extensive leaf senescence. A fungus was isolated from diseased leaves showing typical symptoms of brown leaf spot. The isolates were cultured on potato sucrose agar, and their morphological characteristics of the causal pathogen were observed under a light microscope. Pathogenicity tests revealed that this fungus was the causal pathogen of the disease. Molecular analyses of the sequences of the ribosomal DNA internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (TEF) and the RNA polymerase II second largest subunit (RBP2) gene were conducted to confirm the identity of the pathogen. The multi-gene phylogeny indicated that the causal agent was Alternaria tenuissima. To our knowledge, this is the first report of A. tenuissima causing brown leaf sports on P. polyphylla var. chinensis in China.