Abstract [Background] Recently, the Potato virus Y (PVY) strains breaking down the resistance of va-genotype tobacco varieties have emerged on cultivated tobacco constantly. In 2016, we isolated a va-resistance breaking-down PVY strain, which was named as PVYCJ. This isolate was verified and identified in this study. [Methods] Re-inoculation on the va-genotype tobacco varieties, multiple RTPCR, segmented amplification of the whole PVY genome by RT-PCR, molecular phylogenetic analysis and the sequence alignment of VPg protein of PVY strains were adopted to confirm and identify PVY-CJ strain. [Results] Test data showed: 1) All the 3 va-genotype tobacco varieties showed symptoms of infection when they were inoculated with PVY-CJ inoculum; 2) PVY-CJ was classified as PVYNTN strain according to the result of multiple RT-PCR; 3) Sequence analysis showed that the whole genome of PVY-CJ contained an open reading frame of 9180 nt encoding a polyprotein of 3060 amino acids; 4) the result of molecular phylogenetic analysis further classified PVY-CJ as PVYNTN strain; 5) Compared with other PVYNTN strains, a substitution of lysine to glutamic acid happened at 105 amino acid of VPg protein of PVY-CJ, which led to a breaking down of va-geno source resistance. [Conclusion] We reported and identified a PVY strain which could break down the resistance of va-genotype tobacco varieties in the mainland of China for the first time. This study provides material for breeding new PVY-resistant tobacco varieties.
LI Ruo, LI Zunqiang, WAN Xiuqing, QIAO Chan, GUO Yushuang, PAN Hongxing, CUI Xiao, CHEN Rongping, GUO Zhaokui. Identification of a PVY virus isolate breaking down va-genotype tobacco resistance[J]. Acta Tabacaria Sinica, 2020, 26(4): 72-77.