Occurrence of green mold disease on Dictyophora rubrovolvata caused by Trichoderma koningiopsis

Dictyophora rubrovolvata is an important edible mushroom that is widely cultivated in China. In 2019, a serious rot disease on D. rubrovolvata was observed in a mushroom production facility located in Ce Heng County, Southwest of Guizhou Province, China. The causal agent was identified as Trichoderma koningiopsis by amplification and sequencing of the internal transcribed spacer (ITS) region, the translation elongation factor 1-alpha (EF-1α) gene, and the RNA polymerase II subunit (RPB2) gene followed by phylogenetic analysis. Koch’s postulates were confirmed by a pathogenicity test that was conducted with healthy D. rubrovolvata, including re-isolation and identification. To our knowledge, this is worldwide the first report of T. koningiopsis as a pathogen on D. rubrovolvata causing green mold disease. In addition to crop production that provides the basic nutritional resources for humans, mushrooms have been widely cultivated in Asia for their nutritional value as well as for medicinal applications for over 2000 years (Wang et al. 2020). Dictyophora rubrovolvata M. Zang, D.G. Ji & X.X. Liu, a saprophytic fungus which belongs to the Phallaceae family, is commonly known as “Zhu Sun” (bamboo fungi) in Chinese and “Kinugasatake” in Japanese. The use of this fungus as an edible mushroom can be traced back to the Tang Dynasty in China (Wang et al. 2018) . Due to its high nutritional, medical, and economic value, D. rubrovolvata is currently one of the main edible mushrooms commercially grown in Guizhou Province, China (Ye et al. 2016). It has a unique “umbrella-like” appearance and a crispy structure making it more and more popular in Chinese cuisine. Additionally, various polysaccharides with beneficial properties to health were found to be naturally present in D. rubrovolvata (Wang et al. 2018). This has recently attracted broader attention from consumers and caused an increased demand for traditional functional food. In March, 2019, a serious occurrence of rot disease on D. rubrovolvata was observed in Ceheng County, Guizhou Province, China. Green mold and wilt symptoms appeared on the surface of D. rubrovolvata during the early stages of cultivation (four months), causing direct death or preventing it from forming a sporocarp (Fig. 1A). The disease incidence was 60%-70% on the affected 5.33-ha growing area, causing a serious economic loss. This study was carried out to identify the causal agent of green mold on D. rubrovolvata and to provide relevant background for its sustainable management.