墨白964群体5轮混合选择遗传变异的分子生物学研究

 【目的】研究控制双亲的混合选择法对墨白964群体在四川生态条件下经过5轮适应性改良的效果。【方法】采用性状表型分析和SSR分子标记技术。【结果】经过5轮混合选择后，开花期性状有显著的选择增益, 多数性状的表型变异系数随着选择世代的增加有所下降。40对SSR引物在各轮群体中扩增出418个等位位点，有88.5%的遗传多样性分布于群体内，有11.5%分布于群体间。群体内的遗传多样性大于群体间的遗传多样性，且群体内的遗传差异随着选择的增加呈下降趋势。基因杂合度、多态性位点数和多态性位点百分率都呈递减趋势。原始群体C0的基因型种类多，为418种，且频率分布较散，选择后的高代群体C4、C5的基因型种类少且频率分布较集中。【结论】选择群体的遗传变异逐渐减小，这可能是由于连续对开花期性状定向选择的结果，也可能还与群体的有效含量较小和选择强度大所引起的遗传漂变有关。

The Genetic Diversity Variation Revealed by SSR Markers in the Tropical Maize Population Pob32 After 5 Cycles of Mass Selection

【Objective】The biparental mass selection was used to improve the tropical population Pop. 32 for 5 cycles for photoperiod sensitivity in Sichuan Povince, China.【Method】Phenotype analysis and SSR molecular markers were used in this research.【Result】Results showeds that the traits of flowering were significantly improved after 5 cycles of mass selection. The phenotypic variation coefficients of most of the traits decreased with the advances of generation of selection. With the 40 pairs of SSR markers used, a high level of genetic diversity was in C0 population, a total of 418 alleles were detected in the populations. Some 88.5% of the genetic diversity were estimated intra-populations and 11.5% were estimated inter-populations. The inter-population's genetic diversity was much more than the intra-population's, and the genetic diversity within populations declined with the advances of generation of the selection. The number of polymorphic loci of per population and the ratio of polymorphic loci were also declined as selection. The genotypic numbers of Pop32.C0 was 418, which was the most but the frequency was dispersed. The genotype of Pop32 C4 and Pop32.C5 were small and the frequencies were concentrated. 【Conclusion】The results suggest that the genetic variation declined slowly is possible due to the continuous artificially selection for the early silking and the genetic drift induced by selection intensity or smaller effective population size.