Study On The Genetic Relationship Between Temperate Maize(Zea Mays) Core Germplasms And 27 Domestic And Exotic Populations

Narrow genetic base is one of the major limitation factors for the germplasm development in maize (Zea mays L.) . Maize germplasm enhancement and improvement is the only strategy to broaden the germplasm base and solve the problem of genetic vulnerability. The exotic germplasm, especially the improved tropical and subtropical populations from CIMMYT, is an important resource for maize improvement. These populations are characterized with rich genetic variation and good stress tolerance. Genes from the exotic germplasm may represent unique alleles for productivity that are absent from temperate elite gene pools. In the other hand, the domestic populations in China are characterized with great variation and good adaptability to the environments. Therefore, it would be useful for maize development to reveal the genetic relationship between the temperate standard testers and domestic and exotic populations and introgress the exotic germplams into temperate maize breeding program. The information would be helpful for establishment of correct heterotic groups and heterotic patterns, which is of utmost importance for the improvement with tropical and subtropical germplasm in temperature maize breeding program, and the information only based on the phenotypic characters and ecological types is far insufficient. In the present study, the genetic diversity and genetic relationship of 27 domestic and exotic maize populations was characterized with SSR molecular markers. In the meantime, the populations were crossed with 4 common testers corresponding to the main heterotic groups in China, and the 108 combinations were arranged using NCII design in Kunming, Shenyang, Taiyuan and Yuncheng, and a-Lattice Design was adopted in the field experiments. The potential for maize improvement of the 27 populations were evaluated according to the agronomical characters and combine ability of yield components. At the same time, with the common testers and the heterotic pattern (Mol7XDan340) in spring sowing zone in North China and heterotic pattern (Ye478 X Huangzao 4) in Huang-Huai-Hai summer sowing zone, the genetic relationship of the populations and the core germplasm in China was revealed. The heterotic groups of the populations were classified according to yield SCA, pedigree and molecular data. The results was shown as the following.1. Great genetic variation was found in the 27 populations after SSR marker analysis with the bulking method in which the DNA samples of 4 bulks in each population were consisted of the leaves of 10 seedlings. Populations from CIMMYT had more polymorphic loci than domestic populations. More special alleles were found in CIMMYT populations.2. Genetic similarity coefficients were calculated according to SSR profile data and the dendrogram of the populations was construsted based on UPGMA cluster analysis. The genetic similarity coefficients between the four bulks averaged to 0.91 and varied from 0.86 to 0.96 in the 27 populations, which indicated that the bulked method could be used in the genetic diversity study of the populations.3. According to the means of genetic similarity coefficients and results of cluster analysis, it was found that the domestic populations showed greater genetic similarity than that in exotic populations. Great differentiation between domestic populations and exotic populations was revealed by the genetic...