湿地松样本量大小对性状遗传力估算的影响

摘要

[目的]在保证遗传力估算精确度较高的前提下,探讨对已有湿地松测定群体遗传力评估最经济有效的调查取样数量(样本量),为遗传选择提供最佳的遗传参数和选择策略.[方法]以61个湿地松22年生半同胞家系的胸径、树高等生长性状和木材基本密度、弹性模量等材性性状测定值为试验数据,利用ASReml-R软件混合线性模型的限制性极大似然估计法(REML)估算各性状在不同参试样本量下的遗传力及其标准误.通过比较分析在不同样本量下各性状遗传力及其标准误估算值的收敛性,讨论样本量对性状遗传力估算的影响,进而确定各性状遗传力评估所需的最少样本量.[结果]对于61个湿地松自由授粉家系测定林,当测定的家系数少于39个或者随机测量的单株数小于600株时,估算的遗传力极不稳定,标准误偏大,随着样本容量或家系容量的增加其精度与准确性逐渐增加;遗传力较低的性状其遗传力估计所需样本量普遍大于遗传力较高的性状.[结论]对本研究的测定群体而言,要获得精确度较高的遗传力估算值,所需测定的湿地松家系数应该大于39个或者随机测量的单株数大于600株;由于材性性状遗传力相对较高,其需要测定的样本量可相对少一些.本文为大型用材树种遗传力估算提供了一个具有参考价值的实例研究,结果及相应的研究方法对于类似遗传测定群体遗传参数估算具有参考意义.%[Objective] To determine the amount of slash trial samples for high precision and efficiency of heritability estimation,which provide the optimal genetic parameters and selection strategies for tree breeding.[Method] The growth traits (diameter at breast height and tree height) and the wood properties (basic wood density and modulus of elasticity) of 1 023 sample trees from 61 half-sib families of 22-year-old slash pine (Pinus elliottii) were investigated as the experimental data.Then the heritability of each trait was estimated using Residual Maximum Likelihood (REML) in the flexible mixed modeling program ASReml-R.And the critical or least sample size for heritability estimation of each trait was determined by comparing and analyzing the convergence of the estimated values of heritability and their standard errors under different sample sizes.[Result] (1) In this trial,the estimated values of heritability and their standard errors were extremely unstable when less than 39 families or 600 individuals were used.And the accuracy of these values increased gradually by increasing sample size or family size.(2) The sample size should increase correspondingly in the estimation of the genetic parameters of the traits with low heritability.[Conclusion] In this study,more than 39 families or 600 individuals should be used for the reliable heritability estimation.The sample size for heritability estimation of wood properties could be less because of their high heritability.This paper provides a case study for estimating heritability of timber tree species.The results and the methods for determination of the critical sample size also have reference value for the corresponding study.