Branching habit in radiata pine - breeding goals revisited

Authors: Rowland D. Burdon
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2007, Issue N.Z.J.For. 52(4) 2008, pp 20-23, Jan 2008
Publisher: New Zealand Institute of Forestry

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Abstract: Branching habit necessarily figures prominently in breeding goals for radiata pine in New Zealand. Past breeding has pursued two extremes of regular branch habit: what are effectively short internodes and long internodes respectively. The former, which has featured in the mainstream of the breeding programme, embodies indirect selection to control branch size and angle. However, it does not allow long clear-cuttings without pruning, unlike the latter. Despite much progress towards achieving these two ideotypes, the outcome has not been fully successful. The short-internode option has given insufficient control of branch size, while poor wood stiffness further downgrades the product for structural purposes. The long-internode option, pursuing ‘uninodal’ trees, allows quite long internodal clear-cuttings, but has shown even more than its anticipated drawbacks. Alternative ideotypes now proposed for providing internodal clear-cuttings have two co-equal branch clusters per annual shoot, over a considerable length of bole; branch clusters could be equidistant from each other, or else closely spaced towards the end of the annual shoot. Other possible ideotypes might be favoured for specific site types. Clonal forestry seems necessary to capture such ideotypes, and even then, capturing them poses major challenges. The ability to rejuvenate clonal material at will would be a very powerful tool for this, to avoid prolonged testing of huge numbers of candidate clones.

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