Effect Of Victorivirus FaVV1/2 From Fusarium Asiaticum On Sexual Reproduction Of Hosts

Fusarium head blight is a fungal disease mainly caused by Fusarium graminearum and F.asiaticum.With the global warming and the change of farming methods such as straw returning to the field,the occurrence range of wheat scab in China has gradually expanded from the middle and lower reaches of the Yangtze River to the north and west,and the epidemic frequency has gradually increased.Gibberella not only causes severe yield losses but also toxins such as deoxynivalenol produced by pathogens can affect human and animal health.Chemical control is the main control measure at present,but it is faced with problems such as bacterial resistance and environmental pollution.The low virulence fungal virus can reduce the pathogenicity of host fungi and is a potential source of biological control.A new Victorivirus Fa VV1(Fusarium asiaticum victorivirus 1)was reported from strain F16176 of Fusarium asiaticum,and another Victorivirus named Fa VV2(Fusarium asiaticum victorivirus 2)was found from the same strain in this study.Phylogenetic analysis based on the amino acid sequences of Rd Rp indicated that the two ds RNA viruses were two new members of the genus victorivirus.In addition,a new single-stranded RNA virus of justice was detected from Fusarium graminearum strain CF16158.Phylogenetic analysis of the amino acid sequences of Hel and Rd Rp encoded by the virus indicated that the(+)ss RNA fungal virus was a new member of the alphavirus-like virus family,which we named Fusarium graminearum alphavirus-like virus 1(Fg ALV1).Further studies have shown that Fa VV1,Fa VV2,and Fg ALV1 can reduce the pathogenicity of the host and inhibit the sexual reproduction of the host fusarium,so they have a certain biological potential against scab.Fa VV1 and Fa VV2 viruses could be transferred to wild strains Fusarium asiaticum F0609,F0980,F16176-5?,and Fusarium graminearum PH-1 by protoplast fusion.The colony morphology,perithecium distribution,perithecium size,and ascospore maturity of the virulent strain were observed.It was found that the virus had no significant effect on the colony morphology of the new host,but it could affect the pigment distribution of some host strains.In strains F0609,F0980 and F16176-5? of Fusarium asiaticum,perithecium growth was inhibited and ascospore maturation was prevented.In Fusarium graminearum PH-1,the inhibition effect of perithecium was not obvious.The above results indicated that Victoria virus Fa VV1 and Fa VV2 could affect the sexual reproduction of the host,inhibit the development of perithecium,and inhibit the maturation of ascospores.Therefore,it is necessary to further study the mechanism of Fa VV1 and Fa VV2 viruses inhibiting the sexual reproduction of Fusarium.Ascospores produced by the sexual reproduction of scab are the primary infection sources of wheat scab and play an important role in the infection cycle of scab.Therefore,it is necessary to further study the mechanism of Fa VV1 and Fa VV2 viruses inhibiting the sexual reproduction of Fusarium oxysporum.Generally,the viral shell protein plays a key role in the interaction between the virus and its host.Therefore,in this study,fungal Rp27 was used as the promoter,and the Fa VV1-CP1 and Fa VV2-CP2 protein-coding sequences of the virus were connected,respectively,to construct the viral CP encoding gene expression vector.Mutants of transferrable viral shell protein CP were obtained by pegmediated transformation into wild fusarium type.To observe the effect of CP1 and CP2 on host colony morphology,sexual reproduction,and pathogenicity.The results showed that CP1 and CP2 proteins had no effect on the morphology of host colonies,but had an effect on the distribution of pigment in host colonies.The number of perithecium produced by CP1 strains F0609,F0980,and PH-1 decreased.CP2 strains F0609,F0980,and PH-1 significantly reduced the number of perithecium,or even could not produce perithecium at all.The results showed that both the CP1 protein encoded by Fa VV1 and the CP2 protein encoded by Fa VV2 could inhibit the sexual reproduction of Fusarium graminearum and Fusarium asiaticum.The inhibitory effect of CP protein on the sexual reproduction of Fusarium asiaticum was more significant than that of Fusarium graminearum,and the inhibitory effect of CP2 protein was more significant than that of CP1.The determination of pathogenicity on corn whiskey and wheat ear showed that CP1 and CP2 protein had no significant inhibition on host pathogenicity.In this study,three fungal viruses were identified from Fusarium head blight that could inhibit host sexual reproduction: Fa VV1,Fa VV2,and Fg ALV1.Mycovirus that inhibit sexual reproduction have important biocontrol potential for Fusarium head blight,which plays a key role in the disease cycle.Further studies on the Victorivirus Fa VV1 and Fa VV2 showed that the virus-encoded shell protein CP played a key role in inhibiting the sexual reproduction of the host,which laid a foundation for further research on the molecular mechanism of the virus shell protein inhibiting sexual reproduction of the host.