Data from: Improvement of non-key traits in radiata pine breeding programme when long-term economic importance is uncertain

Diameter at breast height (DBH), wood density (DEN) and predicted modulus of elasticity (PME) are considered as 'key traits' (KT) in the improvement in radiata pine breeding programmes in New Zealand. Any other traits which are also of interest to radiata pine breeders and forest growers are called 'non-key traits' (NKTs). External resin bleeding (ERB), internal checking (IC), number of heartwood rings (NHR) are three such non-key traits which affect wood quality of radiata pine timber. Economic importance of the KTs and NKTs is hard to define in radiata pine breeding programmes due to long rotation period. Desired-gain index (DGIs) and robust selection were proposed to incorporate NKTs into radiata pine breeding programme in order to deal with the uncertainty of economic importance. Four desired-gain indices A-D were proposed in this study. The desired-gain index A (DGI-A) emphasized growth and led to small decrease in ERB and small increase in IC and NHR. The expected genetic gains of all traits in the desired-gain index B (DGI-B) were in the favourable directions (positive genetic gains in the key traits and negative genetic gains in the non-key traits). The desired-gain index C (DGI-C) placed emphasis on wood density, leading to favourable genetic gain in the NKTs but reduced genetic gains for DBH and PME. The desired-gain index D (DGI-D) exerted a bit more emphasis on the non-key traits, leading large favourable reduction in the non-key traits and lower increase in the key traits compared with the other DGIs. When selecting both the key traits and the non-key traits, the average EBVs of six traits were all in the same directions as the expected genetic gains except for DBH in the DGI-D. When the key traits were measured and selected, internal checking always had a negative (favourable) genetic gain but ERB and NHR had unfavourable genetic gain in the most of time. After removing some individuals with high sensitivity to the change of economic weights, robust desired-gain selection made genetic gains of all the key and non-key traits to move a little bit toward unfavourable directions in the four indices. It is concluded that desired-gain index combined with robust selection concept is an efficient way for selecting the key and non-key traits in radiata pine breeding programmes.

在新西兰辐射松育种项目中，胸径（Diameter at breast height, DBH）、木材密度（wood density, DEN）与预测弹性模量（predicted modulus of elasticity, PME）被视为关键性状（key traits, KT）。其他受辐射松育种者与森林经营者关注的性状，被归类为非关键性状（non-key traits, NKTs）。外部树脂溢出（external resin bleeding, ERB）、内部开裂（internal checking, IC）以及心材轮数（number of heartwood rings, NHR）即为三类影响辐射松木材品质的非关键性状。由于辐射松育种轮伐周期较长，难以界定关键性状与非关键性状的经济重要性。为应对经济重要性的不确定性，研究人员提出将非关键性状纳入辐射松育种体系的期望增益指数（desired-gain index, DGIs）与稳健选择方法。
本研究共提出四类期望增益指数A至D（DGI-A至DGI-D）。其中，期望增益指数A（DGI-A）侧重生长性状，可使外部树脂溢出小幅降低，同时导致内部开裂与心材轮数小幅上升。期望增益指数B（DGI-B）下所有性状的预期遗传增益均朝向有利方向：关键性状呈现正向遗传增益，非关键性状则为负向遗传增益。期望增益指数C（DGI-C）以木材密度为选择重点，可使非关键性状获得有利遗传增益，但会降低胸径与预测弹性模量的遗传增益。相较于其余三类期望增益指数，期望增益指数D（DGI-D）对非关键性状的侧重程度更高，可使非关键性状获得大幅有利的遗传降低效果，同时关键性状的增益幅度更低。
当同时对关键性状与非关键性状进行选择时，除期望增益指数D下的胸径外，六项性状的平均估计育种值（Estimated Breeding Values, EBVs）均与预期遗传增益方向一致。仅针对关键性状开展测定与选择时，内部开裂始终呈现负向（有利）遗传增益，而外部树脂溢出与心材轮数在多数情况下呈现不利遗传增益。在剔除部分对经济权重变化敏感性较高的个体后，四类期望增益指数下的稳健期望增益选择均使所有关键与非关键性状的遗传增益略微朝向不利方向偏移。
综上，将期望增益指数与稳健选择理念相结合，是辐射松育种项目中兼顾关键性状与非关键性状选择的有效途径。