Epidemic Identification of Fungal Diseases in Cultivation across China.

True morels (, Pezizales) are world-renowned edible mushrooms (ascocarps) that are widely demanded in international markets. has been successfully artificially cultivated since 2012 in China and is rapidly becoming a new edible mushroom industry occupying up to 16,466 hectares in the 2021-2022 season. However, nearly 25% of the total cultivation area has annually suffered from fungal diseases. While a variety of morel pathogenic fungi have been reported their epidemic characteristics are unknown, particularly in regional or national scales. In this paper, ITS amplicon sequencing and microscopic examination were concurrently performed on the morel ascocarp lesions from 32 sites in 18 provinces across China. Results showed that (75.48%), (5.04%), (0.83%), (0.37%) and (0.15%) were the putative pathogenic fungi. The long, oval, septate conidia of was observed on all ascocarps. Oval asexual spores and sporogenic structures, such as those of , were also detected in infected samples with high ITS read abundance. Seven isolates of were isolated from seven selected ascocarps lesions. The microscopic characteristics of pure cultures of these isolates were consistent with the morphological characteristics of ascocarps lesions. had the highest amplification abundance in 93.75% of the samples, while had the highest amplification abundance in six biological samples (6.25%) of the remaining two sampling sites. The results demonstrate that is a major culprit of morel fungal diseases. Other low-abundance non-host fungi appear to be saprophytic fungi infecting after . This study provides data supporting the morphological and molecular identification and prevention of fungal diseases of morel ascocarps.