Genetic Variability On The Population Of Wheat Dwarf Virus (WDV) In China

Wheat dwarf virus (WDV), transmitted by leafhopper (Psammotettix striatus L.), is a member of the genus Mastrevirus, Geminiviridae. In 2007, our laboratory reported firstly its ocurrence in China. WDV was epidemic extensively in Hancheng, Shaanxi in last year and brought a large reduction of wheat output. Because the great differences in entironment and geography in cereal regions of China, the population of WDV should be abundant variety. The experiments detecting WDV on the wheat and barley from different regions with PCR and ELISA were developed and abroad distribution of the WDV in our country was found.Based on the genome sequence of WDV on GenBank, three pair of special primers was designed. The expected special three segments with overlapping regions were obtained by PCR, and then cloned into the plasmid and sequenced. Total 57 genome sequences were get, in which 47 were from wheat host and 7 from barley host. All of the isolates from the northwest, southwest, Center and North of China possessed the same structure with the reported WDV, which was a circular single-standed (ss)-DNA with 2750nt in length.From the the robust phylogenetic tree, it was concluded as the followings.(1) The isolates were fallen into three subpopulations seemingly structured according to host and geographic origins. One was the WDV on oat, the other was the WDV on barley and the last one was the WDV on wheat. The evolution of WDV on oat was independent. In the clade of WDV on wheat, it was devided into two groups of Chinese and foreign countrys, and it was very interesting that the FR and CZ wheat isolates were basal to those from China. In the clade of barley isolates, the isolates from foreign country were just lonely get. In our research, the nucleotide identities between the seven genome sequences on barley from Kunming. It was seemed the species of WDV on wheat could infect the barley, however it was necessary to focus further on the biological validation.(2) In the clade of WDV on wheat, the Chinese isolates were obviously different from foreign wheat isolates. However, the Chinese wheat isolates were not clustered by geographical source or collection time, while the foreign wheat isolates were clearly clustered by the geographical source except scattered isolates.(3) The isolates from Hancheng, Shijiazhuang, and Kunming possessed abundant diversification for dispersedly existing in the different groups. From the analysis of levels and patterns of intraspecific polymorphism and selective constraints of WDV genes, the population of WDV was in the expansion and the pure selection in the evolutionary proecss. The Rep A gene was most stable than others, then the CP gene was in order, all of the characteristics of molecular variability was being for the changes of environment and hosts. In the Chinese isolates, the diversity of the genes of CP, Rep, Rep A and intergenic regions of LIR, SIR were higher than that of foreign isolates, which only had diversity on the Rep and Rep A gene.