Isolation, Identification and Prevention of Bacterial Spot Disease on Grifola frondosa

<i>Grifola frondosa</i> is a rare fungus valued for its nutritional and medicinal properties; however, its bacterial spot disease has been largely overlooked. Thus, this study systematically investigated, isolated, and identified the pathogen and evaluated control strategies for bacterial spot disease affecting <i>G. frondosa</i> cultivation in Qingyuan County, Zhejiang Province. Through integrated morphological, physiological and biochemical analysis, and multi-locus phylogenetic analyses (16S rRNA, <i>gyrB</i>), <i>Priestia aryabhattai</i> was identified as the causal pathogen. This pathogen exhibited host specificity, infecting only <i>G. frondosa</i> and <i>Pleurotus ostreatus</i>, inducing primordial growth arrest and causing spots on the stipe of mature fruiting bodies. Control assessments revealed significant antimicrobial efficacy for four chemical agents, benziothiazolinone, copper sulfate, ethylicin and tetramycin, three plant extracts, garlic, leek and onion, and two biocontrol strains, <i>Chlorophyllum molybdites</i> and <i>Aspergillus fumigatus</i>. Scanning electron microscopy (SEM) demonstrated that these treatments caused ultrastructural damage to the pathogen's cells, including membrane shrinkage, depression, and perforation. These findings establish key pathogenic characteristics and provide a scientific foundation for integrated disease management, supporting sustainable <i>G. frondosa</i> cultivation.