The Analysis Of The Genetic Variation In 6 Open-improved Maize Populations And The Evaluations Of Breeding Potentialities

In order to improve the shortcomings of maize population P4HSC1,such as ear length was shorter, declined rapidly in genetic diversity, SiChuan Agricultural University Corn Research Institute constructed a number of new open-improved maize populations by importing exogenous germplasm with excellent traits into P4HSC1.In this experiment, we selected the 6 open-improved maize populations of which and P4HSC1,and the 35 combinations as tested materials,the 35 combinations were formed by the seven populations crosses with five standard test inbreds (Huang zaosi, Ye 478,S37, Dan 598 and 18-599).Through field experiments and SSR markers, we analyzed the genetic variation in improved maize populations and their breeding potential, after importing different exogenous germplasm into P4HSC1.The main results were summarized as follows:1,By investigation of agronomic traits, the true genetic differences between most of traits existed among populations, Most of the improved populations' ear length have increased by different degrees,and the bulk density and kernel depth also obtained good relational improvment.The imported germplasm were different, so the improvement results were different between populations.main agronomic economical traits CV of improved populations have increased,that indicated exogenous germplasm can improve effectively target traits of groups, while increasing genetic diversity. But the imported germplasms were different, their improved results were greatly different. SP2's ear height was low, ear length was long,100-kernel weight was higher, and the most of traits were coordinate relatively, the overall level of agronomic traits was highest, but the barren ear tips length was longer, the rows per ear was fewer, and its the frequency of excellent individuals had a slight decline.SP8,SP10 and SP7, their overall level of agronomic traits were intermediate level, the frequency of excellent individuals was higher, but plant and ear height were high. Although SP6's ear length was short, and most of yield traits were low general level,but barren ear tips length was short and kernel depth was deep, the frequency of the excellent individuals was high. SP1's yield traits were lower, and the frequency of excellent individuals was less frequently.2.Populations combining ability analysis showed that plant height, ear height, rows per ear, kernels per row, bulk density of general combining ability (GCA),they have real differences among populations; kernel depth's and yield per plant's special combining ability (SCA) existed real difference between combinations.Germplasm infiltrated by different exogenous, the populations'yield traits GCA were better than the populations' plant traits GCA, kernels per row and bulk density had highlight results in the improvement of GCA,rows per ear GCA decreased, but the vast majority of dynamic improving populations'decreasing trends were not significant. And the imported germplasms were different, their GCA improved effects were also different. Among dynamic improvement populations, SP8 was higher in GCA of ear rows and kernels per row traits,but performance of plant traits GCA were relatively poorer; SP6's rows per ear and test weight of the GCA performed better, but the ear rows and plant traits GCA performance were poor; SP2's bulk density and high GCA ear performed better, but the rest traits GCA performed poor; SP7 most of traits GCA performance average, while the SP1 and SP10's performance of the traits GCA were lower. Through the analysis of the Contrast Superiority,most of combinations that the tested populations combined with Dan 598,whose the yield per plant SCA performed better.3.SSR marker analysis showed that,37 pairs of polymorphisms, clear bands, covering the whole genome of maize SSR primers tested in 7 varying populations of 210 DNA samples per plant, a total of 414 alleles were detected,the per pair of primers detected averagely 11.2 alleles, ranged from 2 to 20. The genetic diversity parameters of improved dynamically populations were revealed more genetic diversity than P4HSC1 by different degrees, but the change of the various parameters was different among populations.Among improvement populations, comparison of the numbers of genotype,maximum was SP1,the least was SP2;comparison of polymorphic alleles and PIC, SP10 was highest, SP2 and SP1 were lowest; the similarity degree between individuals within populations,SP6 was relatively low,SP10 was relatively high; the various genetic diversity parameters of the rest population were in the middle level.4.The distances of 7 maize population were calculated based on data of 14 agronomic traits,7 corn populations were classified into 4 groups,groupâ… included P4HSC1 and SP2, groupâ…¡included SP10 or SP7 and SP8,groupâ…¢included SP6,group iv included SP1. Comparisons of SCA in plant yield in the 35 hybrid combinations with model tester were used as a basis for the classification of heterotic groups. The 7 corn populations were classified into five heterotic groups.The five groups were SP7 and Huang zaosi, SP1 and dan598,SP2 or P4HSC1 and Ye478,SP8 andl8-599,SP10 andS37,SP6 and S37 or 18-599. Comparisons of The genetic similarity (GS) by SSR of 7 corn populations,the 7 corn populations were classified into 3 groups,groupâ… included SP2 or SP7 and SP10, groupâ…¡ included SP1 or SP6 and SP8,groupâ…¢included P4HSC1.In summary, importing exogenous germplasm into population can effectively improve ear length and enhance the genetic diversity of population, at the same,related traits such as grain depth have also improved, most of yield traits GCA had indirect improvements.But the different of imported germplasm,the different of improved results.Overall, SP8 agronomic traits behaved ordinary,but GCA performed relatively well,the excellent individuals frequency within population was high,had comparatively large breeding potential compared with the rest populations.