Cobweb disease on Morchella sextelata caused by Hypomyces spp. in Sichuan province, China

Abstract

Morels (Morchella spp.) are commercially important edible mushrooms with high nutritional and medicinal value. There are more than twenty provinces in China that cultivate Morel mushrooms. As of 2023, white mold disease on cultivated Morchella sextelata has become a disease of concern in Sichuan Province, China, with a disease incidence of 12.13%. The ascocarp infected with white mold disease appears covered with a dense white mycelia of a foreign fungus and disintegrates soon after. However, the causal agent is not yet known. Therefore, this study aims to confirm both the causal pathogen by using Koch's postulates and to further establish, at the species level, the identity of this organism via morphological and molecular methods. The pathogens were later identified as Hypomyces rosellus and Hypomyces aurantius. Healthy ascocarps were inoculated with H. rosellus and H. aurantius, which produced the initial disease symptoms with white mold appearing at the inoculation sites, and H. aurantius showed stronger pathogenicity than H. rosellus; the same pathogens were then isolated again from diseased ascocarp. To our knowledge, this is the first report of the ascocarp cobweb disease of cultivated M. sextelata caused by H. rosellus in China. Our work may be beneficial, especially for designing control measures for ascocarp cobweb disease in the commercial cultivation of M. sextelata.