Three Species, Including a New Species, Cause Wet Bubble Disease of in China.

White button mushroom, (Lange) Imbach, is the most extensively cultivated and edible mushroom worldwide. The production of is commonly affected by wet bubble disease (WBD), imposing a significant economic burden in China. Although studies have shown that this disease is caused by fungi of the genus, the pathogen has not been fully characterized. In this study, 802 samples of diseased fruiting bodies of were collected from nine major mushroom-cultivating provinces in China, yielding a total of 586 isolates. The morphologic characteristics of these isolates were observed and compared, and multilocus phylogenetic analyses (internal transcribed spacer [ITS], , , , , and large ribosomal subunit [LSU]) were performed on the selected representative isolates. Three species were identified: a new species, ; ; and . was the first ever reported in China. Furthermore, was found to be the most prevalent species (54.95% of all isolates) in all the sampled areas, except in Hubei and Xinjiang, followed by (39.93%) and (5.12%). Pathogenicity tests on the fruiting body and mushroom bed substantiated Koch's postulates by the development of mildly different symptoms after inoculation with each species. This study, therefore, enhances our knowledge of the species associated with WBD in and provides useful insights for preventing WBD and allied diseases.