控制双亲的混合选择对热带玉米群体墨白964的改良效应

Effects of Population Improvement by Mass Selection on the Tropical Maize Population MW964

用控制双亲的混合选择法改良MW96 4在四川生态条件下的适应性。经过 4轮混合选择后群体的播种至抽丝日数、播种至散粉日数和雌雄间隔 (ASI)有显著的选择增益 ,株高、雄穗主轴长度、秃尖、穗粗、行粒数、穗重、单株产量和群体产量有显著的相关响应 ,且多数性状的表型变异系数随着选择的进行有所下降。C0 、C1、C2 和C3 测交种群体与对照种比较表明 ,群体各性状的间接选择响应显著 ,多数性状的均值及性状整齐度已接近或超过对照种。此外 ,本文还运用SSR检测了C0 、C2 、C4群体的遗传多样性。发现原始群体C0 的基因型种类多 ,频率分布分散 ,而选择后高代群体C4的基因型种类少 ,频率分布集中 ,且群体内的遗传差异随着选择的进行呈下降趋势。

A tropical population MW964 was improved by bi-parental mass selection for 4 cycles aiming at improvement of the ecological adaptability in Sichuan. Mass selection effectively improved the adaptation of exotic maize population to the local subtropical conditions. The average days to silking and pollen shedding in MW964 were significantly reduced after 4 cycles of selection. Significant correlated responses were found in plant height, main tassel aixs length, barrent ear length, ear diameter, kernel number per row, ear weight, yield per plant and yield per population. The variation coefficients of many traits decreased with selection. Comparisons between CK and four test-crosses (C 0/C 1/C 2/C 3×tester) were shown that many traits of MW964 displayed significant indirect responses to mass selection. The means and the uniformity of these traits were up to or over the level of CK (single-cross). Meanwhile we applied SSR to detect the genetic diversity of the 3 populations (C 0, C 2, C 4). In the 3 populations, the genotypes much more than in Pop. C 0 were in C 4, and the genotypic frequency was dispersed in C 0, while concentrated in C 4. The genetic diversity within populations was declined along with the selection process.