Incorporating economic weights into radiata pine breeding selection decisions

This article introduces the concept of 'robust selection', which proposes tree selection based on the stochastic simulation of economic values to account for the inherent uncertainty of economic weights used in tree selection for breeding programs. The proposed method uses both median ranking and ranking variability as criteria for breeding selection. Using consensus genetic and economic parameters from the New Zealand Radiata Pine Breeding Company program, we compare three selection strategies: deterministic application of economic weights from a vertically integrated bioeconomic model, an equal-weight index often used in operations, and robust selection. All strategies aim to increase value for a breeding objective that includes four traits, i.e., volume, stem sweep, branch size, and wood stiffness (measured as modulus of elasticity), based on a selection index that considers five criteria, i.e., stem diameter at breast height (1.3 m), straightness, branching score, wood density, and modulus of elasticity. Two-thirds of the selected trees were unique for each of the selection strategies. Robust selection achieved the best realised gain for three of the four selection criteria and was the middle performer in the last selection criteria. Considering the high intrinsic uncertainty of economic weights, we suggest that the relevant criterion for the selection of individuals is the maximum median ranking, subject to an acceptable level of variation in that ranking, rather than their narrow performance under a single economic scenario. This will lead to tree selections that perform well under a wide range of economic circumstances. Key words: breeding objectives, economic weights, simulation, economic evaluation, risk analysis. Cet article introduit le concept de << selection robuste >> qui propose une selection fondee sur la simulation stochastique de la valeur economique pour tenir compte de l'incertitude inherente du poids economique utilise pour la selection des arbres dans les programmes d'amelioration. La methode qui est proposee utilise le classement median et la variabilite du classement comme criteres pour la selection. A l'aide de parametres genetiques et economiques du programme de la New Zealand Radiata Pine Breeding Company qui font consensus, nous avons compare trois strategies de selection : l'application deterministique du poids economique provenant d'un modele bioeconomique verticalement integre, un indice de poids equivalent souvent utilise dans les operations et la selection robuste. Toutes les strategies visent a augmenter la valeur d'un objectif d'amelioration qui inclut le volume, la courbure du tronc, la dimension des branches et la rigidite du bois a partir d'un indice de selection qui tient compte du diametre du tronc, de sa rectitude, de la note de branchaison, de la densite du bois et du module d'elasticite. Les deux tiers des arbres selectionnes avec chacune des strategies etaient uniques. La selection robuste a produit le meilleur gain pour trois des quatre criteres de selection et occupe la position intermediaire pour l'autre critere. En tenant compte de l'importante incertitude intrinseque du poids economique, nous suggerons que le critere pertinent pour la selection des individus soit le classement median maximum, qui est sujet a un degre acceptable de variation dans ce classement, plutot que leur performance etroite dans le cadre d'un seul scenario economique. Cela va engendrer la selection d'individus qui performent bien dans une vaste gamme de conditions economiques. [Traduit par la Redaction] Mots-cles : objectifs d'amelioration, poids economique, simulation, evaluation economique, analyse de risques.
Introduction The selection of superior trees is central to breeding programs, aiming to identify individuals with maximum economic-genetic value for a combination of characteristics of economic importance. These trees are [...]