Phylogenetic and morphological characteristics of Alternaria alternata causing leaf spot disease on Camellia sinensis in China

Severe lesions along with black spots on tea leaves were observed in the commercial tea plantations located in Chongqing district of China during the April to July of 2015. The pathogens isolated from diseased tea leaves matched the morphological characteristics of Alternaria alternata that were rarely found on tea plant [Camellia sinensis (L.) O. Kuntze] in all the tea-growing countries worldwide. The characteristics of A. alternata were further confirmed by both pathogenicity tests and multi-gene phylogenetic analyses derived from internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta-tubulin (β-tubulin). The combination of ITS, GAPDH and β-tubulin was more useful for delimitation in the genus Alternaria than any single gene region. Pathogenicity tests conducted on healthy tea leaves showed typical leaf spot symptoms, confirming the role of all the A. alternata isolates as the causal agent of leaf spot disease on tea plants.