Effect Of Population Improvement For Different Cycles Of Yu Syn5 Maize

In China, the narrow of the germplasm genetic base is the prominent question in maize breeding, the population improvement is the efficient way to expand the the germplasm genetic base of our country .This research took five circler populations of Yu Syn5 which were improved by half-Sib recurrent selection and half-Sib reciprocal recurrent selection as material, by the two-site performance test of improvement population's output in one year, simultaneously, using the NC-II genetic design, taking the improvement populations of the Yu Syn5's five circle as the male parent, taking Huangzao4, Dan340, Zhong Syn 5, Qi 319, Ye478, Mo17 as testers to match 30 test crosses through one year two-site appraising test of yied combining ability effect, Yu Syn5 improvement effect was appraised from different angle of a population's output character and the combining ability and so on with recurrent selection. The main results as follows:1. The method of half-half and full-sib recurrent selection could improve t Yu Syn5' yied effectively. To compare C₀ with C₃ , the single average plant's yied of Yu Syn5 was enhanced greatly and reached highly significant probability level; using C₄ comparison C₃, the yied was increased 5.51%. usin every circle of C₁-C₄ comparison C₀, the yied was increased 6.15%, 13.62%, 18.90% and 25.45% respectively, and the average circle was increased 6.36% .2. From the improvement effect of the yied component,comparing C₃ with C₀, the main yied characters were increased, comparing C₄ with C₃, the length of ear tip-barrenness has moderate drop, kernels perrow increased 4.63%. the results indicated that the main yied components were improvedt correspondingly with the enhancement of improvement population , simultaneously . The advantages as follows: the ear to be longer than before, kernels perrow o be more, 100 grains weight to be higher and the maturing stage to be earlier than before, plant height and ear height to be moderate, the good traits had the high latent utilization in the breeding, but the population also had the insufficiency that the era was slender and the number of row per ear lessened. So the traits as highlight should be improved and enhanced.3. Through the analysis of Yu Syn5 improved population coefficient of variation ,the results indicated that the coefficient of variation has slight drop with the increase of improvement circle, the coefficient of variation of the average single plant yied lowered from C₀ 15.43% to C₄ 12.80%, but the individual total of average single yied which above 150g was more than C₀ obviously, the results stated that the improvement population still maintained the higher genetic variation relatively and had the potential of further improvement. The variation coefficient of inproved C₄ ear characters from large to small were 100 grain weight, the number of row per ear, kernels per row, ear length, ear diameter, kernel percentage. therefore, the population had the huge potential in enhancing 100 grain weight and kernels per row.4. The analysis of the average single yied of the 30 test-crosses indicated that the first three high yied test-crosses in the single output were Huangzao 4 as tester accounted for 2, Qi 319 as tester r accounted for1; In the first ten high yied test-crosses were Huangzao 4 as tester accounted for 4, Qi 319 as tester accounted for 3. The lowest three test-crosses respectively were Mo17×Yu C₀, Ye 478×C₀ and Ye 478×C₁, in the low yied test-crosses Ye 478 as tester accounted for 2. The results indicated that Yu Syn5×SiPT was the strongest heterotic pattern , but Syn5×Reid group hybrid was the smallest.5. The analysis of the combining ability effect indicated that after Yu Syn5 was improved 3 circles with the half-sib recurrent selection, the combining ability effect enhanced from -11.63 to 5.57 by C₃ compared with C₀ and reached highly significant probability level; After 1 circle selected with half-sib reciproal recurrent selection, the general combining ability effect enhanced from C₃ 5.57 to C₄ 9.75. the results showed the two methods enhanced the combining ability effect of Yu Syn5. The analysis of special combining ability effect showed that the special combining abilities of improved Yu Syn 5×Huangzao 4 had certain enhancement, which developed steadily toward Reid×SiPT mixed superior pattern.