Analysing Genetic Structure Of Potato Virus Y Pipo Gene

Potato is the third most important food corp worldwide ranking behind the rice and wheat.China is the largest producer of potatoes in the world.Potato virus Y(PVY)is a type member of the Potyvirus genus in the family Potyviridae,which is one of the most important plant viruses causing serious losses of potato crops worldwide.Better knowledge of genetic variation and how the genetic variation is generated and maintained in viral populations is vitally important in developing sustainable management schemes.Nucleotide sequences of pipo gene of potato virus Y(PVY)from different hosts(potato and tobacco)and different regions hosted by potato to compared to investigate the genetic diversity and population differentiation.Meanwhile,mutation,natural selection and gene flow were evaluated to determine evaluated to determine evolutionary forces responsible for genetic diversity and population differentiation.Genetic variation analysis showed that nucleotide identity in pipo gene among the viral isolates from tobacco were 76.5%-100%while that from potato ranged were 93.0%-100%,indicating higher genetic variation in PVY from tobacco than that from potato.The values of gene flow(Nm)between PVY populations from tobacco and potato in pipo gene were 1.83,respectively,suggesting strong gene flow contributes significantly to the population genetic dynamics of PVY population.Neither purifying nor positive selection was detected in pipo gene,indicating neutral evolution of the gene.Similarly,nucleotide diversity(π)and haplotype diversity(Hd)in PVY populations from six provinces were greater than 0.5%,and 0.5,respectively,indicating that a high degree of genetic diversity in these regions.The values of FsT of PVY between Yunnan population and other five populations were greater than 0.15,and those of Shanxi population and other five populations were greater than 0.11,suggesting a moderate genetic differentiation between the populations.KST,Z,and Snn three tests results showed that pairwise population differentiation between the Yunnan population others populations,and Shanxi population and others populations were all significant,indicating a great sptial structure.Neutral tests were negative and highly significant(P<0.05)for Fujian population and Fujian population displayed a unimodal mismatch,suggesting that the population maybe experience a historic expansion event recently.In summary,this study indicated there was a significant genetic variation in PVY from different hosts and regions.Mutation,natural selection and gene flow all contribute to the genetic diversity and population dynamic of the virus.Overall,this study extends our standing the role of biological factors(hosts)and abiotic factors(geography)in evolutionary processes in PVY.