Article ; Online: First Report of Cobweb Disease in Auricularia cornea var. Li. Caused by Hypomyces mycophilus in China
Plant Disease. 2023 Sept. 01, v. 107, no. 9 p.2875-
2023
Abstract: Auricularia cornea var. Li. is a natural mutation strain of A. cornea and has been preferred by consumers for its white color, good taste, and pharmacological properties (Roy 2020). In October 2021, a disease with symptoms similar to those of cobweb ... ...
| Abstract | Auricularia cornea var. Li. is a natural mutation strain of A. cornea and has been preferred by consumers for its white color, good taste, and pharmacological properties (Roy 2020). In October 2021, a disease with symptoms similar to those of cobweb disease (Carrasco et al. 2017) was observed in A. cornea var. Li. in four mushroom farms in Fangshan District (39.55°N, 115.83°E), Beijing, China, infecting 20% of the fruiting bodies. White cottony mycelia formed typically on the casing soil, and they gradually spread to the stipes and pileus, covering the whole fruiting body, which eventually died and lost commodity value. Cultures were obtained by aseptically transferring the diseased fruiting bodies onto potato dextrose agar (PDA); they were deposited in the culture collection (ID: JZBQA3) of the Beijing Academy of Agriculture and Forestry Sciences, China. The colonies were floccose with white aerial mycelium. Purplish gray diffusing pigments occasionally formed on the reverse side of the plate at 25°C. Conidiophores arising from the aerial mycelium had indefinite length and septate branches, where each cell produced denticulate conidiogenous loci and each denticle bore a single conidium. Conidia were mostly oblong to ellipsoidal, smooth, (9.0 to) 9.9 to 17.0 (to 18.0) × (6.0 to) 6.9 to 10.2 μm (n = 60), and 0 to 1 septate. Chlamydospores forming as lateral branches of hyphae were commonly observed, and they were globose, ellipsoid or oblong, 14.8 to 22 × 14.7 to 19.6 μm, and length/width of 1.0 to 1.3. The morphological characteristics were consistent with those of Hypomyces mycophilus, whose anamorph was Cladobotryum polypori (Rogerson and Samuels 1993; Zeng et al. 2017). For further species identification, genomic DNA was extracted using the DNeasy Plant Mini Kit (Qiagen, U.S.A.). The internal transcribed spacer (ITS) regions and large subunit ribosomal RNA (LSU) genes were amplified using the primer pairs ITS1/ITS4 (White et al. 1990) and LROR/LR5 (Bhattacharya et al. 2000), respectively. The sequences were deposited in GenBank with accession numbers OP430530 and OP430531. BLAST nucleotide searches showed more than 99% homology with corresponding sequences of H. mycophilus HMAS 275554 and CBS 175.56. Phylogenetic trees based on ITS and LSU revealed that the strain JZBQA3 grouped with H. mycophilus with high support value. An in vivo pathogenicity test was performed using eight mushroom sticks with healthy fruiting bodies in triplicate. Four sticks were sprayed with a conidial suspension (10⁸ spores/ml) of the strain JZBQA3, the other four sticks were sprayed with sterile distilled water, and all sticks were maintained in an artificial climate chamber at 25 to 26°C. Cobweb-like symptoms were observed on the fruiting bodies treated with the JZBQA3 conidial suspension after 2 to 3 days of inoculation, whereas those treated with sterile distilled water remained symptomless. The same pathogen was reisolated and confirmed from the infected fruiting bodies by integrated analysis of morphological characteristics and gene sequencing data, fulfilling Koch’s postulates. H. mycophilus was first reported on Trametes versicolor in North Carolina (Rogerson and Samuels 1993) and is the causal agent of cobweb disease on A. heimuer (Zhang et al. 2023). To our knowledge, this is the first report of cobweb disease caused by H. mycophilus in A. cornea var. Li. This finding is a valuable contribution to the knowledge of cobweb disease development in edible fungi. |
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| Keywords | Auricularia cornea ; Coriolus versicolor ; DNA ; Hypomyces ; anamorphs ; chlamydospores ; climate ; cobweb disease ; color ; conidia ; conidiophores ; culture media ; forestry ; genes ; hyphae ; internal transcribed spacers ; mushrooms ; mutation ; mycelium ; pathogenicity ; pathogens ; phylogeny ; ribosomal RNA ; soil ; species identification ; taste ; China ; North Carolina ; Cladobotryum ; Hypomyces mycophilus |
| Language | English |
| Dates of publication | 2023-0901 |
| Publishing place | The American Phytopathological Society |
| Document type | Article ; Online |
| ZDB-ID | 754182-x |
| ISSN | 0191-2917 |
| ISSN | 0191-2917 |
| DOI | 10.1094/PDIS-09-22-2214-PDN |
| Database | NAL-Catalogue (AGRICOLA) |
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