Wood Density and Shrinkage of Five-Year-Old Eucalyptus Camaldulensis X E. Globulus Hybrids: Preliminary Assessment (Report‪)‬

Introduction Hybrid eucalypts are being developed for industrial plantations with the aim of producing lines that show hybrid vigour, improved tolerance to biotic and abiotic stresses, or ability to grow under conditions marginal or unsuitable for high-value species such as Eucalyptus globulus (Griffin et al. 2000). Hybrid eucalypts generally have an overall morphology intermediate between that of the parent species with few traits being dominant, but some traits may be closer to those of one parent than the other (Pryor 1954; Pilipenka 1969; Tibbits 1988; Meddings et al. 2003). Wood properties have moderately high heritability (Zobel and van Buitjenen 1989) and have also been shown in hybrids to be generally intermediate between the parents. Wood density and radial shrinkage are traits for which most hybrids appear intermediate (Siarot 1991; Malan 1993, 2000; Verryn 2000) although it is sometimes difficult to make comparisons given data from trees of different ages. There are as yet no examples of useful heterosis in wood properties where the hybrid value is better than that of the best parent. Li et al. (1997) reported quantitative trait loci (QTLs) in two linkage groups that affected wood density in E. grandis.