Preliminary Study On Improvement And Breeding Potential Of Synthetic A/B Maize Population

The lack of maize germplasm resources and narrow Germplasm Base limit the improvement of maize breeding level in China.Population improvement is a common method in the innovation and utilization of Maize Germplasm resources,which creates new germplasm resources for breeding inbred lines to a certain extent.With the introduction of American hybrids and the advent of Reid germplasm selection lines and their derivatives,a large number of excellent hybrids have been bred,which has a great impact on Maize Breeding in China.Southwest breeders constructed group A and B with American elite inbred lines as donor materials and local inbred lines as recipient materials.In this study,the improved populations A,B(recorded as GAC1,GBC1 group)and Enshi station,which added Huayu 11 male parent Q1 and Huayu 11 female parent Q736 on the basis of group A and B(recorded as EAC1 and EBC1group),were used as materials to study the effect of improvement and the two basic populations A/B after two rounds of controlled parental mixed selection for four synthetic populations.The genetic diversity in the process of improvement was analyzed,and the combining ability of four synthetic populations formed after one round of improvement by controlling parents’ mixed selection was tested with six test species.The breeding potential of the population was studied,which provided the basis for efficient utilization of improved population germplasm and selection lines.The main results are as follows:1.The yield of GAC1 increased from 161.89 g to 167.92 g and 6.03 g from the base population C1 to C3 after two rounds of controlled parental mixed selection improvement for four synthetic populations,among which GBC1 increased from167.74 g to 173.36 g and 6.46 g from EAC1 group to C3 group,5.6g from EAC1 group and 4.32 g from EBC1 group.The grain depth,row number per ear,ear length and ear diameter also increased to some extent.2.The hybrid combinations of the population and the test species were tested for significant differences.The traits of different combinations were significantly different at the same place;the traits of the same combination were significantly different at different locations;for the population,there were real differences among the traits among the groups..Through genetic analysis of GAC2,GBC2,EAC2,EBC2 population,the results showed that the plant height and ear height were affected by the environment and by genotype.Studies have also shown that the general combining ability(GCA)variance(%)in the traits examined is higher than the special combining ability(SCA)variance(%),indicating that the effects of additive gene effects play a major role.3.According to the general combining ability(GCA)effect value of yield traits per plant,the general combining ability(GCA)effect value of GBC2 and EBC2 populations was higher than that of GAC2 and EAC2,indicating that B group has more breeding than group A.potential.The special combining ability(SCA)of the Y1027×EBC2 combination was the highest in terms of the special combining ability(SCA)effect per plant yield.4.The number of polymorphic loci,gene heterozygosity,genetic distance and genetic diversity index of A/B group decreased after two rounds of improvement.It shows that the target population can be improved to some extent by controlling the mixed parental selection and continuous directional improvement.