Genetic variation of natural durability traits in Eucalyptus cladocalyx (sugar gum)

Abstract

INTRODUCTION: We present a study on genetic variation in natural durability traits of young-aged Eucalyptus cladocalyx, a species adapted to temperate, low rainfall regions. Our motivation was the production of naturally durable posts for applications such as vine trellises, a sector dominated by heavy metal preservative-treated wood in some of the world’s main wine-producing countries. METHODS: Stem diameter at breast height over- and under-bark, heartwood proportion, wood density, methanol extractives and fungal decay were assessed in a progeny test on a set of 48 families from eight provenances nested within three regions of provenance (ROP) from the species’ natural range. Near-infrared reflectance (NIR) was examined as an efficient assessment method. RESULTS: Strong variation among ROP was indicated for all traits, with low-moderate narrow-sense heritability for growth traits and extractives content and moderate-high heritability of basic density and decay resistance to two of the three fungi. Trait–trait correlations ranged from low to high, with basic density and extractives content being negatively correlated to decay mass loss. DISCUSSION: NIR was an effective predictor of methanol extractives, moderately effective for basic density, but unsuccessful for fungal decay. Generally, there were no practically adverse correlations between growth and durability traits. CONCLUSION: Substantial genetic variation in natural durability traits is indicated, with wide scope for genetic improvement.