Phomopsis vexans, which causes Phomopsis blight of eggplant, has been reported worldwide. To study the biocontrol of this disease, 162 leaf and fruit samples of eggplant Phomopsis blight were collected from Hunan, Hubei, Jiangxi, Sichuan, Zhejiang, Fujian, Guangdong and Anhui Provinces from 2017 to 2019. Eighty-seven pathogenic fungus isolates were identified as P. vexans. The following studies were conducted: screening of sporulation medium, spore morphology analysis, mycovirus detection and identification of novel mycoviruses in these isolates. The results showed that eggplant tissue medium was the most suitable medium for rapid sporulation, and all isolates had mycoviruses consisting of mainly mixed infections. The genome of these mycoviruses varied from 1-15 kb. Five novel mycoviruses infecting P. vexans were obtained, including “Phomopsis vexans fusarivirus 1” (PvFV1), “Phomopsis vexans ourmia-like virus 1” (PvOLV1), “Phomopsis vexans endornavirus 2” (PvEV2), “Phomopsis vexans partitivirus 1” (PvPV1) and “Phomopsis vexans victorivirus L1” (PvVVL1). Thus, PvVVL1 displays a unique genome structure, and this is the first report of a victorivirus consisting of two segments and of a deltapartitivirus infecting the fungus host.
A novel polymycovirus isolating from plant-pathogenic fungus Colletotrichum gloeosporioides was identified. The virus were composed nine RNA segments, ranging from 699 bp to 2,444 bp, and except that RNA5 contains two open reading frames (ORF5-1 and ORF5-2), other RNA segement contain only one ORF. In addition,the proteins encoded by ORFs 1-8 were homologous to the protein encoded by ORFs 1-8 in Colletotrichum camelliae filamentous virus 1(CcFV-1) by BLASTp. The amino acid sequence between the RNA-dependent RNA polymerase (RdRp) encoded by ORF1 and the viral methyltransferase encoded by ORF3 shared 87.6% and 83.3% identity with CcFV-1. The proline-alanine-serine-rich protein (PASrp) encoded by ORF4 shows 86.6% sequence homology to that of CcFV-1. The sequence homology of proteins encoded by ORFs2, 5-1, 6, 7 and 8 with the corresponding proteins of CcFV-1 was 86.6%, 82.5%, 89.0%, 45.7% and 95.5%, respectively. However, RNA9 is a defective RNA of RNA2, missing the 1556 bp (nt 519 to nt 2074) intermediate fragment of RNA2. Phylogenetic analysis based on RdRp protein indicated that the virus, which is the phylogenetically closest relative of CcFV-1, clustered with members of the family Polymycoviridae, so we tentatively named it "Colletotrichum gloeosporioides polymycovirus virus 1" (CgPmV1). To our knowledge, this is the first report of a defective polymycovirus in C. gloeosporioides.
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