Genetic variation in growth, stem straightness and branch thickness in clonal trials of Acacia auriculiformis at three contrasting sites in Vietnam

Acacia auriculiformis has become an important species in Vietnam because it displays adaptability to a wide range of site conditions and produces pulp wood and sawlogs on short rotations. The aim of this study was to estimate genetic parameters and consider implications for development of clonal forestry. Clonal repeatabilities, genotypic correlations, genotype by environment interactions (G × E), genetic selection gains and correlated responses were estimated for total height (HT), diameter at breast height (DBH), stem volume (VOL), straightness (STR), and branch thickness (BRA) measured in three clonal trials of Acacia auriculiformis A. Cunn. ex Benth. in northern, central and southern Vietnam. Assessments were made at age 1, 2 and 3 years on all three trials and also at age 4 years in one of the trials. The estimates of the genetic parameters were based on a total of 130 clones, of which 115 were selected from a progeny test, and 15 were selected from plantations of the Coen River (Queensland, Australia) provenance in Vietnam. Seventy of these clones were planted in all three trials. The clonal repeatabilities for all studied traits increased with age. The repeatabilities at the latest assessment (3 and 4 years old) of the trials ranged from 0.28 to 0.47 for HT, 0.21–0.56 for DBH, 0.21–0.54 for VOL, 0.21–0.32 for STR, and 0.21–0.28 for BRA. Genotypic coefficients of variation ranged from 8.3 to 13.1% for HT and DBH and from 24.6 to 32.6% for VOL. Age–age genotypic correlations were strong for growth traits but ranged more widely from 0.22 to 0.98 for STR and BRA. Straightness and BRA correlated positively with growth traits, with these correlations ranging from 0.13 to 0.76. Low genotypic correlations between the same traits measured in the different trials at age 3 years indicated that G × E was important for this species in Vietnam. Selection of 10% of the clones resulted in gain varying from 14.3 to 23.0% for HT and DBH. Our results indicate that using HT and DBH as selection traits together with STR and BRA would be beneficial in clonal selection of A. auriculiformis for deployment in Vietnam.