Stem rot on Cymbidium ensifolium (Orchidaceae) caused by Fusarium oxysporum in China

AbstractCymbidium ensifolium is an important cultivated herb in southern China. A severe stem rot disease was observed on C. ensifolium in Fujian Province, China, in April 2016. Initially, the junction of the stem and root turned dark black, and the bottom leaves turned yellow. Subsequently, the leaf base began to rot and the stem turned brown and the entire stem became necrotic. A fungus was isolated from diseased stems with typical symptoms of stem rot. The pathogenicity of the isolated fungus was tested with successful infection of inoculated C. ensifolium plants. Koch’s postulates were confirmed by reisolation of the fungus from the infected tissue on artificially inoculated stems. Based on morphological characteristics and sequence analysis of the internal transcribed spacer and actin genes, the pathogen was identified as Fusarium oxysporum. This is the first report of F. oxysporum causing stem rot in C. ensifolium.