| The Sitobion avenae is one of the wheat pests which is frequent and seriously harmful to wheat-producing areas. Regarded as the dominate species during wheat ear stage, they not only lead to production reduction of wheat but also serve as communications media for the barley yellow dwarf virus (BYDV). The damage condition deteriorated with a level from intermittence to frequence in the field since the 70th of last century. There is also an uptrend of amount, duration and area of occurrence. During the evolutionary process, S. avenae not only evolve as a geographical type, but also have unique biotype for the body colour, which are related to its biological characteristics and the changing environmental factors. In this paper, we analyze the the genetic diversity of S. avenae from some wheat areas throughout the China by using the microsatellite markers, considering the three factors: different years, different regions and different colours.By using microsatellite markers, we analyzed the genetic diversity for S. avenae of different body type (mainly red and green) from Beijing( in 2007 and 2008), Hangzhou, Wuhan and Gansu (from 2008) . The results are as follows:(1) A cluster analysis was carried out on S. avenae in different body colour, collected from Beijing in different year. The results showed that individuals in different years were strictly clustered in one class among which Red individuals in 2007 were obviously clustered in one class, and whereas, the red and green ones in 2008 were cross-clustering. The possible reason is extreme weather of the South China in 2008, which affect the insects' moving into these regions and the gene flow among them was rare.(2) A cluster analysis was done on S. avenae in different color types from the four regions in 2008. The result showed that there is a certain difference in clustering atlas between the green and the red for the branches in a relatively close genetic distance. This is mainly because the red is not the dominant species in nature. The particularity fo the red species are amplified when sole cluster analysis was carried out. But it does't go against the genetical principle that body color of different individuals belong to one large genetic type.(3) The test of Linkage disequilibriumd on all the species showed that most of the S. avenae adopt the incomplete cycle reproductive strategy. And this phenomenon varies from one single population to another. So we determined that the body color does not affect the results of linkage disequilibrium.(4) Molecular variance analysis showed that S. avenae's genetic differentiation was mainly due to intraspecies genetic variation. The interspecies variation accounted for a small proportion of total variance. In addition, we found that genetic differentiation between red and green color is not significant, and gene exchange is frequent, which indicates that they have no obvious reproductive isolation, and they may have a similar genetic background.(5) It is found that there is no correlation between genetic differentiation and geographic distances from several sampling points, which means that it is not convincing enough to use the single factor (geographic distances) to explain the genetic differentiation.
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