Strain Group Determination Of Potato Virus Y On Potato In Shandong Pronvince And On Tobacco In Guizhou Province

Potato virus Y?PVY?is an important virus that infects many solanaceous crops including potato?Solanum tuberosum L.?and tobacco?Nicotiana tabacum L.?.It has caused numerous losses in agricultural production.During the long history of Plant-Virus co-evolution,several PVY strain groups have been reported.Several methods have been applied to determine PVY strain groups.However,little information is known about PVY population in China.In this study,PVY infected tobacco and potato leaves samples were collected from Shandong and Guizhou province during2015-2017.Serological,biological and molecular properties of PVY isolates were conducted.The main results are listed as follows:1.Determined the strain groups of PVY isolates infecting potato in Shandong province.A total of 584 field samples and 109 seed potato were collected from the main potato growing area in Shandong province during 2015-2017.ELISA results showed that 515 field samples and 24 seed potato were PVY positive.All the 133selected PVY positive samples can cause veinal necrosis on tobacco.The 5'terminal and 3'terminal of PVY genome of 56 isolates were amplified and sequenced with PVY specific primers.Recombination analysis showed that 51 PVY isolates contain recombination events within P1-encoding region.Phylogenetic analysis based on HCpro-and CP-encoding sequences revealed that 50 isolates have N type HCpro but O type CP,suggesting the obtained PVY isolates are similar genome structure to previous reported PVY^N:O,PVY^N-Wi,and PVY^NTN-NW.To know the complete genome structure,complete genome of seven isolates were obtained.It showed that these seven isolates are most similar to PVY^NTN-NW subgroup.2.Determined the strain groups of PVY isolates infecting potato in Guizhou province.In total,45 tobacco leaf samples were collected from different regions of Guizhou Province.ELISA results showed that about 60%of collected samples were PVY positive.Among them,14 samples were selected and inoculated on 4-6 weeks old tobacco plant.Except isolate CN:GZ5:17 all the samples can induce veinal necrosis on tobacco at 14 dpi.Partial PVY genome of these isolates were obtained with PVY specific primers.Recombination analysis indicated that 11 out of 14 isolate have the recombination events within P1-encoding region.No recombination events was detect within CN:GZ8:16,CN:GZ22:16 and CN:GZ5:17.Phylogenetic analysis based on HCpro and CP-encodng sequence revealed that 13 out of 14 were clustered within HCN and CPO group.Complete genome analysis showed that isolates CN:GZ8:16 and CN:GZ22:16 contain three recombination events,isolates CN:GZ2:16?CN:GZ3:16 and CN:GZ29:16 have four recombination events.The recombination profiles were similar to that of PVY^NTN-NW.3.Analysis of the differences of PVY isolates from different Geographical Origins and different Hosts.Isolates obtained from potato in Shandong province and from tobacco in Guizhou province were analyzed.Sequence comparison showed that most of the isolates from both regions were similar to PVY^NTN-NW group,and have a PVY^O specific epitope recognized by Mab1128.No significant difference was found among PVY isolates from both regions.