Mycoviruses are usually transmitted horizontally via hyphal anastomosis and vertically through sporulation in natural settings. Oyster mushroom spherical virus (OMSV) is a mycovirus that infects Pleurotus ostreatus, with horizontal transmission via hyphal anastomosis. However, whether OMSV can be vertically transmitted is unclear. This study aimed to investigate the transmission characteristics of OMSV to progeny via basidiospores and horizontally to a new host. A total of 37 single-basidiospore offspring were obtained from OMSV-infected P. ostreatus and Pleurotus pulmonarius for Western blot detection of OMSV. The OMSV-carrying rate among monokaryotic isolates was 19% in P. ostreatus and 44% in P. pulmonarius. Then, OMSV-free and OMSV-infected monokaryotic isolates were selected for hybridization with harvested dikaryotic progeny strains. Western blot analyses of the offspring revealed that the OMSV transmission efficiency was 50% in P. ostreatus and 75% in P. pulmonarius, indicating vertical transmission via sexual basidiospores. Furthermore, we observed the horizontal transfer of OMSV from P. pulmonarius to Pleurotus floridanus. OMSV infection in P. floridanus resulted in significant inhibition of mycelial growth and yield loss. This study was novel in reporting the vertical transmission of OMSV through basidiospores, and its infection and pathogenicity in a new host P. floridanus.

Oyster mushroom spherical virus (OMSV) is a mycovirus that inhibits mycelial growth, induces malformation symptoms, and decreases the yield of fruiting bodies in Pleurotus ostreatus. However, the pathogenic mechanism of OMSV infection in P. ostreatus is poorly understood. In this study, RNA sequencing (RNA-seq) was conducted, identifying 354 differentially expressed genes (DEGs) in the mycelium of P. ostreatus during OMSV infection. Verifying the RNA-seq data through quantitative real-time polymerase chain reaction on 15 DEGs confirmed the consistency of gene expression trends. Both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses highlighted the pivotal role of primary metabolic pathways in OMSV infection. Additionally, significant changes were noted in the gene expression levels of carbohydrate-active enzymes (CAZymes), which are crucial for providing the carbohydrates needed for fungal growth, development, and reproduction by degrading renewable lignocellulose. The activities of carboxymethyl cellulase, laccase, and amylase decreased, whereas chitinase activity increased, suggesting a potential mechanism by which OMSV influenced mycelial growth through modulating CAZyme activities. Therefore, this study provided insights into the pathogenic mechanisms triggered by OMSV in P. ostreatus.

Cordyceps militaris is an important medicinal and edible fungus that contains a wide range of bioactive ingredients, including cordycepin, polysaccharides, ergosterol, mannitol, proteins, and carotenoids, which collectively confer tonic, anti-fatigue, immunopotentiating, antioxidant, anti-inflammatory, and metabolic-regulating properties. Notably, the culture residue of C. militaris, which remains rich in bioactive compounds, is mostly discarded during production, resulting in resource waste and potential environmental pollution. In this study, C. militaris culture residue extract (CME) was prepared by ultrasonic extraction, and its antiviral activity was evaluated using Nicotiana benthamiana via foliar spraying. The results showed that CME treatment significantly upregulated the expression of defense-related genes PR1, PR2, and ICS1, with PR1 showing the most pronounced induction (13.20-fold before and 11.89-fold after TMV inoculation), thereby conferring strong antiviral activity. In addition, root irrigation with 10 mg/mL CME significantly increased plant height, stem diameter, dry weight, fresh weight, chlorophyll content, and carotenoid content in tomato plants. Taken together, these findings indicate that CME functions as a plant immune inducer capable of effectively suppressing tobacco viral diseases while promoting plant growth. This study not only provides a new strategy for the value-added reutilization of C. militaris culture residues but also offers a scientific basis for the green control of tobacco mosaic disease.