Research On Hypovirulent-Associated Mycovirus In Cotton Verticillium DAHLIAE Vd08284

Verticillium dahliae Kleb. is the causal fungal agent of Verticillium wilt disease and it has become the most devastating pathogen in cotton production. With an aim to develop biological control agents of Cotton Verticillium wilt disease in the future, we investigated for the presence of viruses that may infect the fungus.Total51hypovirulence isolates which were pathogenicity tested from162V.dahliae isolates originally collected from three cotton-planting regions in China were creened for the presence of dsRNA. The result showed that only one isolate Vd08284carried with2dsRNAs.The dsRNA segments were cloned by modified technique of random amplification of whole RNA sequences. Two sequences were determined by cDNA sequencing and termed dsRNAl and dsRNA2. The complete sequence of dsRNAl is1768bp long (accession no. KC422244.1), and dsRNA2is1587bp long (accession no. KC422243.1). The deduced protein encoded by dsRNAl contains characteristic sequence motifs of putative RNA-dependent RNA polymerases (RdRP). A Blast-P search of this protein showed65%-85%identity with RdRPs of seven known fungal partitiviruses:BfPV1, DdV1, DdV2, OPV1, GaRV-MS1, PsV-S and AoV1. The deduced sequence of the major ORF in dsRNA2encoded a putative coat protein (CP). Multiple protein sequence alignment of the CP amino acid sequence showed52%-63%sequence identity with those of the partitiviruses BfPV1, DdV1, DdV2and PsV-S. So, this mycovirus was designated Verticillium dahliae partitivirus1(VdPV1). Two phylogenetic trees were generated by aligning their respective RdRP or CP amino acid sequences, the VdPV1sequences, and virus sequences from different menbers of Partitiviridae, Totiviridae and Chrysoviridae families. This phylogram revealed that VdPV1was clustered with the members of family Partitiviridae, but distant from the members of the families Totiviridae and Chrysoviridae. It indicated that the VdPVl is a new mycovirus belonging to the family Partitiviridae.30strains containing VdPV1mycovirus have obtained successfully by using confront culture between isolate Vd08284and strain T692marked with hygromycin, it is decidable that mycovirus VdPV1has horizontal transfer capabilities in Verticillium dahliae. Through them biological characteristics, and found that most of the strains pathogenicity, mycelial growth rate and crude toxin secretion was significantly reduced. It may be concluded that if V.dahliae has been infected mycovirus VdPV1, its pathogenicity will be declined. Thus, it can infer that the mycovirus VdPV1has potential of biocontrol. In the future study, there are more work should to be done before the mycovirus VdPV1used as biological control agent.