Black root rot caused by Thielaviopsis basicola on Korean ginseng seedlings grown for the fresh salad market

The consumption of fresh young Korean ginseng roots in salads has recently increased in Korea. In July 2014, black root rot was observed on ginseng roots grown under hydroponic conditions in Ulsan, South Korea. Diseased roots first developed red lesions, which eventually became black. The typical symptoms included yellowing of the plants, stunting and wilting, reddish-brown lenticels, and black lesions on the roots. Sequencing of the internal transcribed spacer rRNA gene region and phylogenetic analysis confirmed that the isolates were Thielaviopsis basicola. Koch’s postulates were supported by pathogenicity tests conducted on healthy plants. Based on morphological characteristics, pathogenicity tests on host plants, and molecular analysis, the causal fungus was identified as T. basicola. This is the first report of black root rot caused by T. basicola on Korean ginseng. The recent occurrence of the disease indicates that the fungus poses a potential threat to fresh ginseng production in Korea.