The Genetic Effect Of Continuous Divergent Selection In Cross-Bred Population Of Wheat(Triticum AestivumL)

A base population was established through multi-parent crossing by using Taigu dominant male-sterile wheat, and then five cycles of 2-way selection for four quantitative characters were conducted. The dynamic changes of genetic structures in the open-pollinated wheat population were examined by RAPD technique, and the divergence of agronomic characters was studied by quantitative analysis. The results of quantitative analysis of agronomic characters showed each selective character basically made progress in correspondence to the way as expected. Selection also caused the divergence among the characters, which were not selected. The selective effect was evident for the selection of increasing the height of plant, and both increasing and decreasing the density of spikelet. Accompany with the selection of plant height, some correlations among characters changed. According to the results of multiple regression analysis and correlation analysis, the number of grains per plant. the kernel weight per head and the number of kernels per head had significant effects on the grain yield per plant. 7 primers in RAPD analysis amplified 116 sites. The results of gene frequencies and phenotypic bands showed abundant genetic variations existed in the population. The percentage of polymoiphic loci was 88.79, and the average heterzygosity was 0.3143 in the whole population. The genetic distance of RAPD showed (1) The genetic distance within a subpopulation was lower than that between every two subpopulations. ?Each subpopulation had considerable divergence compared with unselected population. The genetic distances between the subpopulations, which were selected for plant height, gradually increased accompanied with the selection. I4DThe genetic distance between subpopulations, which were selected for the same character, was lower than that were selected for different characters both in the same generation and among different generations. The cluster results of RAPD genetic distance demonstrated that the subpopulations selected for the same character going to one cluster. It also showed that the selective effect of increasing plant height was obvious.