利用SSR标记分析玉米轮回选择群体的遗传多样性

利用SSR标记技术分析了玉米基础群体DC0及其选择两轮后的群体HSC2和MSC2以及基础群体XFC0和其选择一轮后的群体XFC1的遗传多样性。结果表明：49对引物在5个玉米群体中共扩增出185个等位位点，每个SSR座位的等位基因数目为1～7个，平均为3．8个；基础群体多态性位点总数和多态性位点比例比其改良群体的略高；DC0、HSC2和MSC2 3个群体的基因平均杂合度相似，XFC0与XFC1的基因平均杂合度相似；基础群体与改良群体的平均遗传距离也相似；累加各引物扩增的基因型种类，改良群体的基因型种类偏少，但这些差异均不显著。以上结果说明轮回选择的基础群体与其改良后群体的遗传变异相似，轮回选择可以保持群体的遗传变异范围，改变群体的遗传组成，增加群体内个体间的异质性。

Genetic Diversity Analysis of Maize Recurrent Selection Populations by SSR Marker

Two cycles of mass (MS) and half-sib (HS) recurrent selction and one cycle of marker-assisted selection (MAS) for yield were carried out in two synthetic maize populations DC_0 and XFC_0,respectively.The genetic diversity of five maize (Zea mays L.) populations,including basic population DC_0 and its developed populations HSC_2,MSC_2,and basic population XFC_0 and its developed populations XFC_1,were evaluated by 49 SSR primers,which are averagely distributed on 10 maize chromosomes.On the 49 SSR loci,a total of 185 alleles had been detected in these populations.At each locus,1 to 7 alleles could be detected,with an average of 3.8.The proportion of polymorphic sites differed in the five maize populations,which were 90.3%,85.9%,84.9%,85.9%,80.5% for DC_0,HSC_2,MSC_2,XFC_0 and XFC_1,respectively.Genotypes can be showed by the difference of the alleles detected on the 49 SSR loci.There were totally 430,392,377,399 and 395 genotypes for DC_0,HSC_2,MSC_2,XFC_0 and XFC_1,respectively.The mean gene heterozygosity calculated from the 185 alleles were 0.660,0.644,0.645,0.662 and 0.655 for DC_0,HSC_2,MSC_2,XFC_0 and XFC_1,respectively.All these results mean that after selection the ranges of variance of the populations decreased slightly.And the mean genetic distance calculated from the 185 alleles were 0.4695,0.4696,0.4698,0.4836 and 0.4902 for DC_0,HSC_2,MSC_2,XFC_0 and XFC_1,respectively.There was nearly no difference after selection in both the basic populations.Analyses on the distribution of genetic distance showed that most of the genetic distances in the developed populations were smaller than in the basic populations.But the ranges of the genetic distance were wider after selection in both populations.This result indicated that heterogeneity between some of the individuals in the developed populations increased after several times of recombination and exchange.All these indexes demonstrated that the genetic diversity of selection populations was similar to their primary populations,and genetic variation was maintained during recurrent selection.