棉花良种提纯复壮不仅仅是单纯防止种子混杂退化,保持一个品种的原来面貌,而且要在防止混杂退化的基础上,不断提高种性,推陈出新,使良种不断完善和提高。1972年以前,我县主要是开展群众性提纯复壮,首先解决混杂退化问题,混杂退化基本解决后,我们就注意抓岱字棉15号的系统选育,提高其种性。我们把克服岱字棉出苗差、苗期长势弱、成熟晚的缺点作为主攻方向,进行定向系统选育,淘汰退化的变异,巩固原有优良性状的遗传,加强有益变异的选择,不断巩固提高当班品种,取得了良好效果。我们主要抓了:(一)改多中选优为优中选优与多中选优相结合:原种生产,单株选择是基础,原种质量高低,关键是单株选择的好坏。按照传统的原种繁育程序,在原种圃中选单株,选出的单株数量多,但决选率不高;种子量少,不 Purification and rejuvenation of elite varieties of cotton is not only simply to prevent the hybrid seed from degeneration, maintain the original appearance of a variety, but also to prevent hybrid degeneration on the basis of continuous improvement of species, innovation, so that continuous improvement and improved varieties. Before 1972, our county mainly carried out mass purifying and rejuvenating. First, it solved the problem of mixed degeneration. After the basic solution of mixed degeneration, we focused on the systematic breeding of Dai Dai Zi No.15 and increased its species. We will overcome the Dai word cotton seedling poor seedling weak, mature late as the main direction of shortcomings, directional system selection, elimination of the degradation of the variation, to consolidate the inheritance of the original fine traits, to strengthen the choice of beneficial mutation, and constantly consolidate and improve Duty classes, and achieved good results. We mainly focus on: (A) change in the election for the optimal selection of superior and multi-selected combination of superiority: the production of primary species, single plant selection is the basis of the quality of the original species, the key is the choice of single plant is good or bad. According to the traditional seed breeding program, the original nursery selected single plant, the number of selected single plant, but the decision is not high; less seed, not