比值性状的遗传力与选择强度的关系

利用模拟技术比较不同遗传参数组合下比值性状的理论遗传力及其各选择强度下实现遗传力的差异,证明比值性状的遗传特性与一般正态数量性状不同,其实现遗传力随选择强度不同而呈有规律的顺序变化,并且这种变化受构成比值的两个分量性状的遗传力和遗传相关大小影响。Sutherland的理论遗传力同样不能有效地预测选择比值的遗传变化。反求指数法(IIR法)对直接选择比值的作用机制分析表明:不同选择强度下,作用于比值的两个分量性状上的相对选择压不同,呈非线性方式变化,由此造成比值实现遗传力的改变和遗传改进方式不一样。这些结果为深入认识比值性状的遗传特性和育种工作中有效地提高这类性状提供了依据。

RELATIONSPIP BE WEEN HERITAB LITY OE A RATIO AND SELECTION LNTENSITY

Realized heritabilities at various selection intensities and Sutherland ,s expected heritability for a trait (R) defined as a ratio of two component traits were compared for the parameter populations studied by Monte Carlo simulation technigae. The result showed that the realized heritabilities of a ratio changed in a seguential fashion dependent upon the selection intensity and which was affacted by heritabilities of component traits and genetic correlation between two component traits. This changing he ritability is contrary to previous concepts for a normal trsit that a heritability is a constant for a population. Sutherland's expected heritability also con nat predict the genetic change in Reffectively. The relative selection weights placed on the two component traits, determined by using the Index-In-Retrospect ( IIR) procedure, changed in a non-linear fashion, which demonstrated that the genetic change in R would be in different ways account for the selection intensity.