First report of root rot of Chinese yam caused by Pythium ultimum var. ultimum in China.
In May 2014, in Heze City, Shandong Province, China, the stem base of Chinese yam [Dioscorea polystachya] seedlings showed water-soaked lesions, and the fibrous roots also showed hygrophanous lesions. Three Pythium-like strains were isolated from the roots and stems of Chinese yam with disease symptoms by using general tissue separation on V8 selective media. The three isolates all were identified as P. ultimum var. ultimum [Globisporangium ultimum] based on the morphological characteristics, sequence analysis of portions of the cytochrome c oxidase subunit I gene and pathogenicity tests. This is thought to be the first report of root rot on Chinese yam caused by P. ultimum var. ultimum in China.