Genetic variation in traits affecting sawn timber recovery in plantation grown Eucalyptus nitens

Abstract

Introduction - There is increasing interest in managing Eucalyptus nitens plantations for sawn-timber production. Aims - This study aimed to determine the potential for genetic improvement of traits affecting green sawn-board recovery in plantation grown E. nitens. Methods - The study was undertaken on an E. nitens progeny trial. All trees were measured for DBH and stem straightness and 560 trees were selected for timber processing. Assessment was made of survival, log and green sawn-board volume, log-taper and both upper and lower log end-splitting. Genetic variation in and between these traits was estimated. Results - Genetic differences among races were significant for DBH at years nine and fourteen, stem straightness, log-taper and green sawn-board volume. Within-race, narrow-sense heritabilities were significant for DBH, stem straightness, log volume and both upper and lower log end-splitting. Positive and significant additive genetic correlations were observed between DBH at all ages and survival, stem straightness and log volume. Significant adverse genetic correlations were shown between upper log end-splitting and DBH at years nine and fourteen. Conclusion - These findings showed that harvest-age stem straightness and log volume objective traits in E. nitens are amenable to genetic improvement and that selection for early-age DBH in breeding programs should improve harvest-age survival, stem diameter and straightness, as well as log and green sawn-board volume. However, these improvements are likely to be countered to some extent by increased end-splitting of logs from larger trees.