An experimental comparison of selection alternatives to plateaued response.
An experimental comparison of selection alternatives to plateaued response.
复制标题
选择替代方案与稳定响应的实验比较。
作者：
W. P. Brown;A. Bell
三种替代选择方法，延长选择限制或打破反应高原进行了比较，在一个重复的模型实验中，使用两个不相关的种群的果蝇，不再回应纯种选择高蛋数，杂种优势多基因性状。这三种方法分别是：（1）相互轮回选择（RRS），在每个稳定群体内的选择仅基于杂交性能，（2）相互轮回选择（MRRS）的修改，在每个群体内的选择基于纯种和杂交性能，和（3）在通过杂交两个稳定群体形成的新合成群体内的纯种选择。对各平台群体的纯系产蛋数的遗传力进行了估计。实现的遗传力值和估计的差异分析表明，两个群体的加性遗传变异的情况下，然而，传统的组内相关方法的估计是积极的。方差分析表明，各群体的纯系产蛋数均存在显著的非加性基因效应，而杂交产蛋数的显著基因效应为加性基因效应。两个基础群体的纯种和杂交蛋数之间的遗传相关估计为负（-0.85 +/- 0.68和-0.32 +/- 0.25）。所有三个替代方案，继续纯种选择了显着的反应，与平均增益每一代从MRRS显着上级其他两种方法。RRS下观察到的纯种和杂交反应与数量遗传理论一致。但MRRS的情况并非如此，它表明可能存在主基因分离。证据支持纯种和杂交性能之间的负遗传相关性和超显性的可能性，并进行了讨论。
Three alternative selection methods for extending selection limits or breaking response plateaus were compared over ten generations in a replicated model experiment using two unrelated populations of Drosophila melanogaster that no longer responded to purebred selection for high egg number, a heterotic polygenic trait. The three methods were: (1) reciprocal recurrent selection (RRS) with selection within each of the plateaued populations based solely on crossbred performance, (2) a modification of reciprocal recurrent selection (MRRS) with selection within each population based on both purebred and crossbred performance, and (3) purebred selection within a new synthetic population formed by crossing the two plateaued populations.--Conflicting estimates were obtained for heritability of purebred egg number in each of the plateaued populations. The realized heritability values and estimates from diallel analyses indicated an absence of additive genetic variation for both populations; however, estimates from conventional intraclass correlation methods were positive. The diallel analyses revealed significant amounts of nonadditive gene effects for purebred egg number in each population, while the significant gene effects for crossbred egg numbers were additive. Estimates of the genetic correlation between purebred and crossbred egg number were negative (-0.85 +/- 0.68 and -0.32 +/- 0.25) for the two base populations.--All three alternatives to continued purebred selection gave significant responses, with the average gain per generation from MRRS being significantly superior to the other two methods. Observed purebred and crossbred responses under RRS were in agreement with quantitative genetic theory. Such was not the case for MRRS, which suggested the possibility of major gene segregation.--Evidence supporting a negative genetic correlation between purebred and crossbred performance and the possibility of overdominance is presented and discussed.