| In the study the material, were 60 individuals from 2 synthesized com populations and 180 combinations derived form crosses to 3 testers based on an incomplete diallel disign. These materials were provided by SiChuan Agricultural University Corn Research Institute and SiChuan Academy of Agricultural sciences. The genetic variation Of the 60 individuals was evaluated by SSR primers, the GCA of 60 individuals and the SCA of 180 combinations of major agronomic economic traits were evaluated in an incomplete diallel disign. The main results were summarized as follows:1. Variance was significant in all the observed traits except for kernel depth in the 180 crosses (Table 1). Analysis of combing ability in traits with significant variations in the two seasons showed that GCA and SCA variance was significant in traits except for Row/ear SCA (Table 2).2. The results of 60 individuals GCA showed that the number of GCA effect significant at 0.05 or 0.01 was different in different traits, the number was much except plant height and ear height. And the GCA of GP-5 S2 were better than GP-4 S2 in most traits except kernels per row in economic traits (Table 3 ). Comparisons the number of strains in which 3 individuals GCA effect were significant at 0.05 or 0.01. In economic traits the number was much more than in agronomic traits, the variations was higher in Row/ear, Kemels/ row, Ear.weight and Yield/plant.3. The results of 20 strains GCA showed that in most of the traits there was much variations among different strains in the same population except plant height and ear height (Table 4). The strains 55,57,89 in GP-4 S2 and 93,105,107 in GP-5 S2 had more breeding potential because of, high field GCA effect and most positive economic traits GCA effect. In three testers, 48-2 had higher GCA effect in most agronomic and economic traits, so 48-2 had more potential crossed with GP-4 S2 and GP-5 S2 (Table 5).4. The results of 180 crosses SCA showed that there were different hybrid numbers of SCA effect significant at 0.05 or 0.01 level in different traits. In the same traits there were different hybrid numbers in different S2 of populations (Table 6). Comparisons the 20 hybrids which were superiority over CK 8%, the individuals from the strains 89,57,73 105,107 had more possibility to obtain high field hybrids crossed with 48-2 (Table 7).5. The genetic diversity of the 60 individuals were evaluated with 40 SSR primers, which are distributed on the 10 maize chromosomes. At the 40 SSR loci, a total of 420 alleles were detected in the 60 individuals. At each locus, 3 to 25 alleles could be detected, with an average of 10.5. The indexes including polymorphic site number, ratio of polymorphic sites and genotype number in GP-5 S2 were all higher than those in GP-4 S2 (Table 8), so GP-5 S2 was more polymorphic than GP-4 S2. It was shown in the table 9 that the average gene heterozygosity in GP-5 S2 was higher than that in GP-4 S2. This result not only showed there was more abundant genetic diversity in GP-5 S2, but also indicated that the inbred progenies of GP-5 became homozygous slower.6. The average genetic distance between GP-4 S2 and GP-5 S2 was 0.609, The average genetic distance among the 20 strains was 0.532,The average genetic distance among the individuals within the same strain was 0.065 (Tablel0), So the average genetic distance between GP-4 S2 and GP-5 S2 was higher than that among the 20 strains, and the average genetic distance among the 20 strains was also much higher than that among the different individuals in the same strain. The 60 individuals were classified into 5 groups and 10 subgroups according to genetic distance (Table 11 and Pic 3), the 3 individuals in a strain were classified together, it showed that the genetic difference between them was less. The 30 individuals in GP-4 S2 most divided into theâ… andâ…¢group, the 30 individuals in GP-5 S2 some strains from GP-4 S2 and GP-5 S2 were classified into the same subgroup, It indicated that these strains may have the same genetic backgrounds.It concluded that the GCA of GP-5 S2 was better than GP-4 S2 in most traits, and the GP-5 S2 was more genetic variation than GP-4 S2 by SSRs. There was much GCA variation among different strains in the same population, and the genetic variation among the 20 strains was also much higher than that among the different individuals in the same strain by SSRs. In order to improve the efficiency, when selecting inbred lines from synthetic population, the more individuals should be selected to test combing ability in early generation. The strains 55,57,89 in GP-4 S2 and 93,105,107 in GP-5 S2 had more breeding potential because of high field GCA effect and most positive economic traits GCA effect. |
