Clonostachys Species Associated with White Mold Disease of Cultivated Morels in China

Morels ( Morchella spp.) are among the most widely cultivated edible mushrooms in China, but rapid expansion of production has been accompanied by rising incidence of white mold disease (WMD), reducing yields. Although more than 10 fungi have been reported associated with WMD, the diversity and distribution of causal agents remain unclear. In this study, 832 diseased fruiting bodies of Morchella importuna , M. sextelata , and M. septimelata were collected from 64 locations across 16 major morel-producing provinces in China. Sixty Clonostachys isolates were recovered and identified using morphological traits and multilocus phylogenetic analyses, confirming four species: C. chloroleuca , C. farinosa , C. rosea , and C. solani . Of these, C. chloroleuca and C. farinosa were reported for the first time on morels in China. Clonostachys rosea was dominant (81.7% of isolates), widely distributed, and induced mold symptoms in the pathogenicity test. In contrast, C. chloroleuca , C. farinosa , and C. solani showed comparatively lower frequencies and pathogenicity. These findings broaden the understanding of Clonostachys diversity associated with WMD and provide a foundation for developing integrated management strategies in commercial morel production.