尾叶桉与赤桉正反析因交配杂种F_1材性遗传参数的估算

目的]通过尾叶桉与赤桉杂种F1材质性状的遗传参数估算及其分析,为桉树杂交育种材性改良亲本选配和交配设计提供理论依据。方法]以尾叶桉与赤桉6×6正反析因交配杂种F1测定林为材料,并以相应亲本自由授粉的半同胞子代作对照。9年生时,对各小区的杂种和家系(5株小区,6次重复)选取2株平均木,在胸高1. 3 m处沿南北向钻取木芯,共984个,测定木材基本密度、纤维长、纤维宽和纤维长宽比,利用ASReml-R估算4个材质指标的特殊配合力、杂种优势、父母本单株狭义遗传力、遗传相关和表型相关系数。结果]表明:尾叶桉与赤桉正反交的杂种木材基本密度优于对照,呈明显的杂种优势;反交组合杂种其木材基本密度优于正交组合杂种,正交组合杂种的纤维特性优于反交组合的;在正交组合杂种中,木材基本密度、纤维长和纤维长宽比的母本效应低于父本效应;而反交组合杂种中,4个材质指标的母本效应均高于父本效应。木材基本密度和纤维特性指标受中至低遗传控制。正反交组合杂种中,除纤维长宽比外,其余3个材质指标的显性效应大于加性效应。对于遗传相关,杂种的木材基本密度与纤维宽呈极显著的负相关,与纤维长宽比呈极显著的正相关,与纤维长呈不显著负相关,纤维长与纤维宽呈显著正相关。对于表型相关,除纤维宽与纤维长宽比呈不显著正相关外,其余性状间均呈极显著正相关。结论]尾叶桉与赤桉杂种的材质性状遗传差异因亲本和交配方式而异,表明通过种间杂交和正向选择进行材质性状的遗传改良具有潜力。

Genetic Parameters for Wood Properties in a Reciprocal Factorial Mating Design between Eucalyptus urophylla and E. camaldulensis

Objective] To estimate the genetic parameters for wood properties of Eucalyptus urophylla (U) and E. camaldulensis (C) F₁ hybrids and provide a theoretical basis for the selection of parental genotypes and mating design for the improvement on wood properties of eucalypts.Method] A trial involving 36 reciprocal crosses from six C parents and six U parents preselected for superior growth and stem straightness was built. Ten open-pollinated (OP) half-sib families using the hybrid parents as females were included as the controls. The wood basic density (BD), fibre length (FL), fibre width (FW) and FL/FW at age 9 were assessed with 2 average stand trees from every 5 tree plot, 984 wood cores were drilled for 82 combinations with 6 repeatations, at the height of 1.3 meters along the north to south. Specific combining ability, heterosis, single tree''s narrow-sense heritability (h²) for female and male, genetic and phenotypic correlation coefficient were estimated for four wood property traits by ASReml-R.Result] Inter-specific hybrids generally performed better than the OP progenies in terms of BD, which showed a significant heterosis. Female C by male U crosses (C×U) generally outperformed those involving female U by male C (U×C) in terms of BD, whilst, U×C crosses generally outperformed those C×U in terms of FL, FW and FL/FW. The maternal effects of wood basic density, fibre length and FL/FW were lower than paternal effects in U×C crosses, whilst the maternal effects of four wood properties were higher than paternal effects in C×U crosses. The h² estimates based on general hybridizing ability for BD and fibre traits were generally middle to low. Except for FL/FW, the dominance variance of all the other three wood properties were larger than additive variance. The ratio of hybrid dominance to additive variance (σ_D²/σ_A²) were larger than 1 for BD, FL and FW. The trait-trait genetic correlations amongst hybrids were significant and negative between BD and FW, significant and positive between BD and FL/FW, whilst, not significant and negative between BD and FL, and significant and positive between FL and FW. However, The trait-trait phenotypic correlations between wood properties were significant and positive except that between FW and FL/FW.Conclusion] Genetic parameters of U and C hybrids in terms of wood properties are different from parental genotypes and mating direction, and inter-specific hybrid breeding and forward reciprocal selection is feasible for the improvement of wood properties.