Very early selection for solid wood quality: screening for early winners
This article reviews the theoretical basis for indirect selection – where early selection is an example – and how correlated response is calculated. The review is followed by a description of issues as to the choice of selection criteria that could explain the lack of substantial progress on breeding for wood quality. These include: the autoregressive nature of selection criteria, overemphasizing the importance of basic density as selection criterion, ignoring age-related trends of wood properties, using rotation age rather than technical thresholds as objective traits and ignoring that not all grades have identical marginal economic value. Three data sets are either analyzed for the first time or reanalyzed under different assumptions, to explore the importance of these criticisms. Finally, the use of critical value thresholds as very early selection criteria is suggested and discussed in the context of improving intrinsic corewood quality.