Studies On The DsRNA Virus Of Pleurotus Ostreatus And Virus-Free Strain

ABSTRACT The genomes of dsRNA viruses infecting Pleurotus ostreatus were isolated from the mycelia of Pleurotus ostreatus and had 4 segments by the dsRNA technique.The sizes of the dsRNAs were 8.2kbp,2.0kbp,1.1kbp(according to the calculation BioCaptMW sorftware).The sample was treated with DNaseⅠ,S1 Nuclease and RNAase A,and was proved to be dsRNA.The 8.2kbp of the dsRNA genomes was doublet.The partial dsRNA genomes were cloned and sequenced by one-step RT-PCR. The sizes of RT-PCR were 556bp and 351bp from the 2.6kb and 8.2kb,respectively. The deduced amino acid sequence of the 556bp was very similar to Pleurotus ostreatus virusⅠ(PoVⅠ)by blast and alignment of conserved motifs in RdRp.The nucleotide identities was 86%and the amino acid identities was 94%.9 amino acids among the difference 10 amino acids in which 7 amino acids were positive were not in the conserved motifs and only one was in the V tentative superpositions of conserved motifs in the RdRp.As a result,the 2.6kb code the RdRp,which was similar to Partitiviridae.So the dsRNA genomes might belong to Partitiviridae.Though CsC1 gradient centrifugation the purified virus preparations contained isometric particle of 27～28nm in diameter and 22～24nm spherical particle.The 22～24nm spherical particle was first reported.Base on those studies the virus-free prparation experiment which repeatedly cut the 3-4mm tender mycelia of the edge of the colony to be cultured in the 32-34℃was performed.The average growth rate of the virus-free strain was 1.2 times that of the control strain and the biomass of the virus-free strain was 2.8 times that of the control strain.In contrast to the control strain the product of the first flush of the virus-flee strain was almostly equal and the one of the second flush of the virus-free strain increased by 10.9%.The virus-free strain developed in the shape of sporophores.The caps of the virus-free strain were bigger and the average width was about 13cm and 8cm in length.The Fruitbodies were fleshy and neat.But the caps of the control strain were smaller and the average width was about 10cm and 6cm in length.Fruitbodies were thinner and different in the sizes.