The Molecular Research Of Genetic Variation Of 5 Cycles Mass Selection In The Tropical Maize Population MW964

A -tropical population MW964 was under biparental mass selection for 5 cycles. The object of this selection method was improvement of its adaptability to the local environmental conditions in Sichuan. The research results of phenotype and molecular markers were obtained as follows:1. From phenotype analysis, we can draw a conclusion, after 5 cycle biparental mass selection; the mean days to silking and shed pollen in MW964 were significantly reduced. Per cycle for silking was shortened by 0.71 days, and per cycle for shedding pollen was shortened by 0.30 days. The ASI (anthesis-silking interval) per cycle was shortened by 0.41 days conrespontedly. Significantly correlated responses are found in other traits such as mature period, barrent, ear diameter, ear weight, kernel numbers per row, axis diameter, axis weight, kernel deepness, and yield per population. The phenotype variation coefficients of many traits decreased with the selection.2. The genetic diversity index, this experiment screened 40 pairs' primers with good extending effect and good diversity from 85 pairs primers. The genetic diversity index was calculated by polymorphism alleles of 40 pairs' primers. The genetic diversity index of population Co changes from 0.5527 to 2.756, the average is 1.891, and that of Pop.C1 changes from 0 to 2.643, the average is 1.730. That of Pop.C2 changes from 0 to 2.536, the average is 1.658. That of Pop.C3 changes from 0 to 2.583, the average is 1.608. That of PopC4 changes from 0 to 2.438, the average is 1.579. That of Pop.C5 changes from 0 to 2.421, the average is 1.482. 88.5% genetic diversity distributes in intra-population and 11.5% in inter-population. The inter-population's genetic diversity is more than the intra-population's and the genetic diversity within populations declined along with the selection process.3. The average genetic distance(GD), the GD of Co, C1, C2, C3, C4, C5 were 0.488, 0.480, 0.502, 0.475, 0.436, 0.423 respectively. Of them, the GD of Pop.C2 was the biggest and that of Pop.C5 was the smallest.4. The genie heterosity of per populations was 0.793(C0), 0.781(Ci), 0.755(C2), 0.763(C3), 0.752(C4), 0.727(C5) respectively. The factual select imprument .(-0.013) was consisted with the line correlate response (-0.012), (R2=0.957). These demonstrate the genetic diversity declined with the selection increasing cycles.375. The number of polymorphic loci and ratio of polymorphic loci. This experiment amplified 418 alleles by 40 pairs SSR primers. The number of polymorphic loci of per populations was 386(C0), 316(Ci), 304(C2), 293(C3), 283(C4), 267(C5) respectively and the ratio of polymorphic loci was 88.0%(C0), 75.6%(Ci), 72.7%(C2), 70.1%(C3), 67.7%(C4), 63.9%(Cs) respectively. They declined along with the selection process.6. The comparation of the genotypes and that of the frequency of genotype. The genotypical numbers of Pop.Co was 418, which was the most but its frequency was dispersed. And that of the Pop d, C2, C3, C4, C5 was 412, 382, 357, 317, 318 respectively. Due to the continuous, oriented selection for the flowering traits and the genetic drift induced by selection intensity or effective population size the genotype of Pop.C4 and Pop.CS were small and the frequencies were concentrated.