Phylogeography Of Agropyron Cristatum Species Inferred From The Pgk1 Gene

Agropyron cristatum (L.) Gaertner is the typical species within the genus Agropyron Gaertner. It is indigenous to the steppe region of European Russia and southwestern Siberia. A. cristatum have many useful traits, such as tolerance to drought, low temperature, and salinity, and resistance to rusts, head scab, and other pathogens of wheat (Triticum aestivum L.), thus being a valuable resource for the improvement of some crop species. Previous study mainly focused on the development and utilization of A. cristatum. However, there are still many unsolved questions to be answered from the perspective of population genetics, such as the genetic diversity and genetic structure. In this study, we choose Pgkl gene as molecular marker to do a Phylogeography research of A. cristatum from four groups, through the population biodiversity analysis, population genetic structure analysis and phylogenetic analysis speculated the evolutionary history of A. cristatum. The mainly conclusions are as follows:1. Two hundred and eighty-six sequences were obtained from the materials. Six hundred and ninety variation sites were detected and 265 haplotypes were recovered. Nucleotide diversity and haplotype diversity are 71=0.02070, and Hd=0.99902 respectively. It also revealed 14.943% of the total variation resided among populations, and 85.057% resided within populations.2. The value of genetic diversity and genetic distance between central Asia group and other groups indicated that the central Asia group had higher genetic diversity (π=0.02220, Hd=0.99830) and the genetic distance is very closely with other three groups. It suggested that the central Asia was the central for biological diversity of A. cristatum.3. Network analysis showed that sequences fall into two obvious branches. Clade 1 includes haplotypes from parts of the Tibetan Plateau group, the Central Asia group, and the East Asia group. Clade 2 contained the European group and parts of the Tibetan Plateau group, the Central Asia group, and the East Asia group. Haplotypes of Tibetan Plateau group and Central Asia group are located in inside position of Clade 1 and Clade 2, respectively, and appear star-shaped radiation towards edges. It had been pointed out that the haplotype that originated in the modern appears at the edges of network figure and the haplotype that originated in ancient mostly appears at the interior of network figure. Based on this we can infer that the Tibetan Plateau and Central Asia may be the refuge of wheatgrass during the last glacial period.4. Tajima’D test result showed that A. cristatum in European populations is 0.04456 (P> 0.10), the result doesn’t significant, and follows the neutral evolution model, which indicates that A. cristatum in the European group didn’t take place population expansion event in the history of evolution. But the Tajima’D test results of the Tibetan Plateau, Central Asia and East Asia showed that these three regions have experienced a population expansion event. Combined with Nm date and Fst date we could infer that existing pedigree geographical structure of A. cristatum may be due to Central Asia group diffused to East Asia, the Tibetan Plateau and Europe after the glacial period, it also involved the formation of the European group directly; Tibetan Plateau group diffused to East and Central Asia, it exchanged gene with Central Asia group so that exchanged gene with the European group indirectly, and formed through in this way.