Genetic variation in growth and stem straightness in Eucalyptus saligna trials in Fujian

Abstract

Summary Trials of two groups of Eucalyptus saligna families, with 84 open-pollinated families representing nine natural stand provenances from Australia, were established at three sites in central and northern Fujian province in 2002. At age 3.5 y (about half the average rotation length for eucalypt plantations in south-eastern China) these were assessed for tree growth, stem straightness, branching habit and self-pruning ability, whilst cold tolerance was assessed at the coolest site at about age 3 y. Significant differences were observed in some of the trials variously between provenances and families-within-provenances for growth (average tree volume), stem and branch form traits and cold tolerance. Average individual-tree volume was sensitively dependent on both genetics and environment—tree volume among trial sites varied up to six-fold, but within any one trial, average tree volume of the best provenance was only about 30% above that of the poorest provenance. The magnitude of variation between families-within-provenances was generally greater and more often significant than the variation between provenances—especially for average tree volume. The magnitude of variations observed for stem and branch form traits were generally minor. At the coldest site, some significant provenance differences were also found for cold tolerance. Estimates of within-provenance individual-tree heritability for individual-tree volume ranged from 0.00 to 0.21 ± 0.12 and those for stem straightness, branching habit and self-pruning ability ranged from 0.00 to 0.10±0.09. A number of provenances tested ranked highly for average tree volume at one or more sites but performance across sites was generally not consistent and significant site x provenance interactions were found for both volume and stem straightness. For volume the site x family-within-provenance interaction was also significant. Consequently, definitive conclusions regarding provenance potential could not made, though a provenance from Blackdown Tableland in Queensland was notable for combining good growth and cold tolerance. It was concluded that the best path for genetic improvement of E. saligna in such environments would involve vegetative clonal propagation of the best individual trees, regardless of provenance or family, for commercial plantation deployment; acquiring a wider sample of provenances and families of this species from higher-elevation, summer-rainfall areas (e.g. tablelands of northern NSW and Queensland) to expand the breeding population; and initiating sublines within the breeding population for markedly different target environments.