控制双亲混合选择对2个玉米窄基群体主要性状的改良效果

【目的】研究5轮控制双亲混合选择对2个玉米人工合成窄基群体P3C0和P4C0的改良效果,为玉米群体的有效改良及育种利用提供理论依据。【方法】在不同生态条件下,对群体主要性状进行表型鉴定,并按不完全双列杂交模型进行配合力测定。【结果】控制双亲混合选择对群体单株产量和主要构成性状及其一般配合力(GCA)改良效果明显,但对群体与测验种的特殊配合力(SCA)却没有明显的改良效果。基础群体P3C0及其改良后代,粒深和穗行数均以C0为最小,C5为最大,其GCA分别以C2和C5为最大;单株产量及其GCA都以C0为最小,分别以C4和C2为最大。基础群体P4C0及其改良群体,粒深和穗行数均以C0为最小,分别以C5和C4为最大,其GCA都以C4为最大,单株产量及其GCA都以C0为最小,分别以C2和C4为最大。改良群体其它多数性状及其GCA也都大于C0,不同群体的同一性状及同一群体的不同性状,在不同的改良轮次,其改良效果不尽相同。总体趋势表现为,控制双亲混合选择进行到一定世代后,群体一些性状及其GCA能得到同步有效改良,有些性状自身及其GCA的改良效果却不同步。当选择响应到达最大以后,持续的控制双亲混合选择则会导致窄基群体的选择增益下降,甚至出现负增益。此外,在群体容量为600株,入选率为10%的情况下,经5轮选择后,群体仍保持了较丰富的遗传变异。【结论】在改良窄基群体时,除应适当控制改良轮次外,还应处理好各性状的关系,做到有主有从,主从结合,并定期研究群体改良效果,针对群体存在问题,适当调整改良方案。对于产量和相关性状及其GCA已得到较好改良的群体,可根据杂优模式将群体配对,采用群体间相互轮回选择,在改良群体GCA和SCA同时,使种质改良与杂交种选育紧密结合,以提高群体改良利用效率。

Effects of Biparental Mass Selection on Two Narrow-Base Maize Populations

【Objective】 Two synthetic narrow-base maize populations, P3C0 and P4C0, were improved by 5 cycles of biparental mass selection, the effects on the population per se and combining ability were analyzed with the objective to make suggestions on how to raise the efficiency of improvement and utilization of synthetic populations. 【Method】 In different ecological environment, the phenotype of the populations per se were analyzed, and the combining ability were tested according to an incomplete diallel model.【Result】 Most traits of the populations per se and the GCA were improved significantly, whereas the SCA of most traits showed no significant increase over biparental mass selection. For P3C0 and its improved descendants, the mean of kernel depth and rows per ear were smallest at C0 and largest at C5. The GCA effects of them were smallest at C0, and largest at C2 and C5, respectively. The yield per plant of populations per se and its GCA effects were both smallest at C0, and largest at C4 and C2, respectively. For P4C0 and its improved descendants, the mean of kernel depth and rows per ear were smallest at C0, and largest at C5 and C4, respectively. The GCA effects of them were both smallest at C0, and largest at C4. The yield per plant of the populations per se and its GCA effects were both smallest at C0, and largest at C2 and C4, respectively. For most of the other traits per se and their GCA effects, the improved descendants were larger than their respective C0. There were different effects of improvement on different populations and traits at different cycles. The general trend showed that after cycles of biparental mass selection, some traits of populations per se and their GCA were improved simultaneously, while the improvement of population per se and the GCA did not display a synchronicity for some others. After the largest selection response to biparental mass selection was obtained, a sustained biparental mass selection would lead to a decrease in genetic gain or even a negative genetic gain. In addition, the populations retained their genetic diversity over 5 cycles of biparental mass selection with a population size of 600 plants and a selective ratio of 10%. 【Conclusion】 The improvement effect of the populations should be analyzed periodically, then adjust the improvement program according to the results. It is necessary to coordinate the relationship of the directly selected traits and the remaining traits in a narrow-base population improvement program via recurrent selection. When the major traits of population per se and GCA are improved effectively, a reciprocal recurrent selection method should be employed to improve the GCA and SCA synchronously, and then the germplasm improvement could combine with hybrid breeding.