Stipe Canker Caused by Trichothecium roseum on the Edible Shaggy Mane Coprinus comatus in China

Coprinus comatus, the shaggy mane, is one of the most popular and widely cultivated edible mushrooms in China. Its young fruiting body has good nutritional and medicinal value as well as a special flavor. In July 2010, an unusual stipe rot symptom was observed in cultivation tunnels in Pingyin county of Shandong Province. The lower part of the stipe was infected and water soaked scab occurred. The scab then expanded, a few mycelia and pink spores emerged on the scab surface, and finally, the stipe decayed and the fruiting body became wilted. The pathogen was isolated from infected tissues of C. comatus and the colonies on CYM were whitish at first, then pink sorus emerged, later forming concentric rings of sporulation. Mycelia were floccose, colorless, slender, and septate. Conidiophores bore upright, nonbranched, and colorless sporogenous cells, and slightly rounded spores were borne on the top and aggregated in pink cephaloid. Conidia were obovoid or obpyriform. Almost all spores were two-celled and one septate, while one was nearly round and the other bore an apex (1). The size of spores ranged from 10 to 21 μm long and 5 to 7 μm wide, which was consistent with the characteristics of Trichothecium roseum (1). The species identification was confirmed by sequencing the ribosomal ITS sequences. The ribosomal ITS1-5.8S-ITS2 region was amplified from the isolated strain using primers ITS1 and ITS4. A BLAST search in GenBank revealed the highest similarity (99%) to T. roseum (JQ434580). Pathogenicity was tested on different parts of 20 fruiting bodies of C. comatus with or without the wound treatment. One inoculum was prepared by flooding the agar surface with sterilized double distilled water for spore suspension (6.5 × 10³ conidia/ml), and the other was by 0.2 × 0.2 cm mycelial plugs without spore production on CYM at 25°C for 5 days. After 1 to 2 days, only inoculated stipes showed water soaked and slight decay on the injured surface of all 20 fruiting bodies, while control fruiting bodies remained healthy. The symptoms were similar to those observed in the cultivation tunnels. No symptom was observed on the pileus, either with or without wound treatment. Pathogens reisolated from the inoculated stipes were confirmed to be T. roseum based on morphological characteristics. Because T. roseum is generally regarded as a postharvest disease of fruits and vegetables such as apple, pear, and muskmelon (2), apples and pears were inoculated with this fungus as well using the same methods. The parts inoculated were sunken, wettish, and decayed with brown stain at 25°C and 90% relative humidity after 5 days. Thus, it was confirmed that the T. roseum from the C. comatus stipe canker could infect the fruits of apple and pear. To our knowledge, this is the first report that T. roseum can cause disease on agaric.References: (1) G. Dal Bello. Australas. Plant Dis. Notes 3:103, 2008. (2) J.-H. Kwon et al. Plant Pathol. J. 26:296, 2010.