Preliminary Studies on the Effects of Oyster Mushroom Spherical Virus China Strain on the Mycelial Growth and Fruiting Body Yield of the Edible Mushroom Pleurotus ostreatus.

Abstract

Simple SummaryOyster mushroom spherical virus (OMSV) is a positive-sense single-stranded RNA mycovirus which is associated with a devastating oyster mushroom die-back disease. However, little is known about its classification, and the effects of OMSV infection on its fungal host remain unclear. In the present study, we present the molecular evidence that virus isolates from the P. ostreatus 8129 strain in China represent a new strain of OMSV, named OMSV-Ch. Phylogenetic analysis based on the putative replication protein (RP) suggest that the OMSV may belong to a new yet-to-be-established genus of the Tymoviridae. Using single hyphal tip cultures combined with high-temperature treatment, we obtained the OMSV-Ch-cured P. ostreatus strain. Preliminary studies indicate that OMSV-Ch infection can significantly inhibit mycelial growth, cause malformation symptoms, and reduce the yield of the fruiting bodies of the edible mushroom P. ostreatus. Furthermore, OMSV-Ch can horizontally transfer to a virus-cured strain.Oyster mushroom spherical virus (OMSV) is a positive-sense single-stranded RNA mycovirus which is associated with a devastating oyster mushroom die-back disease. However, little is known about its diversity, and the effects of OMSV infection on its fungal host are not well understood. In this study, we determined the nearly complete nucleotide sequence of OMSV isolated from cultivated oyster mushrooms in China. Sequence analysis suggested that the virus represents a new strain of OMSV (referred to here as OMSV-Ch). A GenBank BLAST search of the genomic sequences demonstrated that the OMSV-Ch had the highest identity (74.9%) with the OMSV from Korea (OMSV-Kr). At the amino acid–sequence level, these two strains shared 84.1% identity in putative replication protein (RP) and 94.1% identity in coat protein (CP). Phylogenetic analysis based on RP showed that OMSV-Ch clustered with OMSV-Kr, closely related to Tymoviridae. Phylogenetic analysis based on both the RP and CP showed that OMSV had a distant clade relationship with tymoviruses, marafiviruses, and maculaviruses. We obtained the OMSV-Ch-free Pleurotus ostreatus strain via single hyphal tip cultures combined with high-temperature treatment. Preliminary studies indicate that OMSV-Ch can significantly inhibit mycelial growth, cause malformations of the fruiting bodies, and reduce the yield of P. ostreatus. Co-cultivation resulted in horizontal transmission of the OMSV-Ch to a virus-cured strain. The findings of our study contribute to the prevention and control of mycoviral diseases in the future.