Identification and characterization of a new species, Cladobotryum hypsigum, that causes cobweb disease in beech mushroom (Hypsizygus marmoreus) in Korea

Symptoms similar to the cobweb disease were observed on beech mushrooms (Hypsizygus marmoreus') growing in Cheongdo-gun, Gyeongbuk Province, Korea, in May 2013. The causal agent was collected and cultured on potato dextrose agar media at different temperatures (5-30°C). The growth of the isolated fungus, characterized by the production of numerous sclerotia and red pigments, was temperature dependent, with minimum growth at 5°C and maximum growth at 25°C. A pathogenicity test revealed that the isolated fungus causes cobweb disease in the host mushroom H. marmoreus (white) as well as in three other mushrooms-H. marmoreus (brown), Flammulina velutipes, and Pleurotus eryngii-with massive mycelia and few conidia. Phylogenetic analysis of four genes (ITS, RPB1, RPB2, and TEF) showed that this isolate has a unique lineage and is distantly related to other species of Cladobotryum that cause the cobweb disease. The results showed that the isolated fungus is a new species, herein named Cladobotryum hypsigum, which causes cobweb disease in H. marmoreus in Korea.