自花授粉作物育种中分离世代的选择效应

SELECTION EFFECTS IN SEGREGATING GENERATIONS OF BREEDING POPULATION FOR SELF-FERTILIZED CROPS

将Cockerham的加性一显性遗传模型以及无限群体在自交下的亲属间方差一协方差系统,推广应用于有限育种群体.着重从理论上分析了分离世代的选择对于后代纯系的平均数和遗传方差的影响.结果表明,遗传力较低的数量性状亦应在自交第1-2代(组合问)或第2-3代(组合内)即开始选择。其选择响应可达到最大选择响应(即自交∞代纯合群体的选择响应)的80％左右;同时,遗传方差仅略有降低,使选择群体仍保持着相当的选择潜势.提高选择响应的关键在于加强环境控制,改进遗传力.显性的存在对选择影响甚小.

Cockerham's additive-dominance genetic model and his variance—covariance system between relatives under selling are applied to a finite breeding population. The effects of selection in segregating generations on the mean and variance of recombinant homozygous lines are discussed analytically. The results indicate that the selections between crosses and within crosses could be started in the 1st—2nd and 2nd-3rd generations of selfing respectively, even if the traits under consideration are quantitative characters with low heritability. The selection may have about 80% of the maximum response, which could be reached by selection among fixed homozygous lines after ∞ generations of selfing. On the other hand, the genetic variance will decline slightly and a considerable proportion of genetic variation remains in the population for the further selection. The heritability is the most important component for the response of early selection in segregating generations. The influence of dominance on the selection is limited.