A new species of Mariannaea isolated from the fruiting bodies of Morchella sextelata in Hebei Province, China

Morels (Morchella spp.), as rare and economically valuable edible mushrooms, have been rapidly cultivated in China and other regions in recent years, becoming a significant part of the agricultural economy. However, with the expansion of cultivation areas, morel diseases have become increasingly prominent. In particular, the white mold disease outbreak has severely restricted yield and quality improvement. A novel species (Mariannaea parasitica) and a new record of Mariannaea (Mariannaea parasitica) are reported from white mold-diseased fruiting bodies of Morchella based on morphology and phylogenetic analysis of ITS and LSU. The new species is characterized by erect, septate, hyaline, irregularly branched conidiophores, which often bear verticillate branches and usually produce 3–6 phialides. The phialides are ampulliform-lageniform, while the conidia are hyaline, smooth-walled, ellipsoidal to ovoid, with one side concave or flattened. This study broadens our understanding of the diversity of pathogen species in cultivated morels.