A Preliminary Study On A New Double-stranded RNA Virus And Its Effect On The Biological Characteristics Of Its Host Beauveria Bassiana

This study was carried out from the aspects of the isolation and identification of wild Beauveria bassiana strains,the determination of biological characteristics and virulence against insect pests,the identification of new fungal viruses and the biological effects of new viruses on B.bassiana.The results are as follows:(1)There are significant differences in spore production,spore germination rate,colony growth rate and virulence to Ostrinia furnacalis among wild strains of B.bassiana.The colony growth rate of B.bassiana was positively correlated with its virulence,but the spore germination rate was not correlated with its virulence,but the spore production was negatively correlated with its virulence.Therefore,the colony growth rate of B.bassiana can be used as a preliminary evaluation index for rapid screening of highly virulent strains of B.bassiana.(2)A new double-stranded RNA(ds RNA)fungal virus was isolated,and its genome was composed of four ds RNA genomic fragments,namely 3441 bp,2779bp,2925 bp and 2688 bp.The first fragment encodes the RNA-dependent RNA polymerase(Rd Rp)gene.It was confirmed that the virus was a new member of Chrysovirus and named Beauveria bassiana chrysovirus 2(Bb CV2).And upload the NCBI database(NCBI: txid2810134).(3)After detoxification induced by low temperature,the virus-harboring strain was obtained and the virus-free strain was obtained.It was found that the colony of the virus-carrying strain was significantly larger than that of the virus-free strain,and the LT50 of the virus-carrying strain was longer than that of the non-virus strain LT50.It was preliminarily determined that the virus could increase the colony growth rate of B.bassiana and reduce the virulence of B.bassiana.In summary,this study made it clear that the virulence of B.bassiana against pests was positively correlated with the colony growth rate,which could be used as a preliminary index for the screening of high virulent strains,it was helpful to improve the screening efficiency of excellent strains.A new strain of Chrysovirus,Beauveria bassiana chrysovirus 2,was isolated and identified from B.bassiana,which established ability to increase the colony growth rate of B.bassiana while reduce the virulence of B.bassiana.