巨桉第二代家系遗传变异及优良家系选择

Genetic Variation and Selection Among Second Generation Families of Eucalyptus grandis

通过对141个巨桉第二代家系的生长特性对遗传变异性和优良家系进行评估,结果表明:巨桉生长性状极差和标准差随着林龄的增加而增大,说明林分随着林龄的增加,生长性状的两极分化越大,树高、胸径的变异系数范围均小于0.5,单株材积变异系数则大于0.5;在不同月龄巨桉的比对中,生长性状的表型变异系数均大于遗传变异系数,随着树龄的增加,巨桉的生长性状受到遗传力的控制就越小;不同月龄巨桉生长性状受低至中等水平的遗传控制,同一月龄内,生长性状的家系遗传力均大于单株遗传力,家系整体遗传力表现为0.2~0.7,单株遗传力在0.15~0.69之间。以3个生长性状胸径(D)、树高(H)和单株材积(V)指标构建巨桉家系及单株性状选择指数方程,按照标准选择出了16个优良家系和65株优良单株,入选率分别为11.35%和5.34%,入选单株的遗传增益均小于家系的遗传增益,但整体表现在合理的范围内,表明选择效果显著。

Based on the growth characteristics of 141 second generation families of Eucalyptus grandis,the genetic variation among families was evaluated.The results showed that the range and standard deviation of growth traits of E.grandis increased as stand age increased,indicating that the polarization of growth traits increased with increasing stand age.The variation coefficients of tree height and DBH were less than 0.5,while the variation coefficient of individual volume was more than 0.5.In comparing E.grandis at different ages,the coefficient of phenotypic variation of growth traits was greater than that of genetic variation.With the increase of tree age,the growth traits of E.grandis were less controlled by heritability and at different ages heritabilities of such traits were of a low to medium level.Within the same age,the heritabilities for growth traits of families were greater than those of individuals.The family heritabilities were within the range 0.2~0.7,while those of single trees were between 0.15~0.69.An index equation for selection of superior E.grandis families and individuals within families was constructed using three growth traits DBH,H and V,and using this 16 excellent families and 65 excellent individual trees were selected with selection rates of 11.4%and 5.3%respectively.Estimated genetic gains for individual tree selection were less than those from family selection,but the overall performance was within a reasonable range,indicating that the selection effect was significant.