Genetic Variation of Physical and Chemical Wood Properties of Eucalyptus globulus

Abstract

This study considered the degree of genetic variation for diameter (DBH), basic density (BD), predicted pulp yield (PPY), fibre length (FL), microfibril angle (MFA) and cellulose content (CC) amongst eight subraces of Eucalyptus globulus growing in a field trial in NW Tasmania. There were significant subrace effects for BD, FL and CC. This variation affected the relative profitability of the subraces for pulp production. On average, the most profitable subraces (on NPV/ha over the base population mean) were Strzelecki Ranges ($862.04), Western Otways ($657.80) and Strzelecki Foothills ($576.81). The genetic control (heritability) of variation in DBH, FL and MFA was moderate (0.15 < h2< 0.27), while control for BD, PPY and CC was high (h2> 0.40). Genetic correlations between growth and wood properties were not statistically significant, except for DBHMFA (-0.86). Most genetic correlations amongst wood properties were outside the parametric space (< -1 or >1), but there were significant correlations between BDMFA (-0.70) and PPY-CC (0.82). The empirical response to selection on an index based on a pulp wood objective (which included volume and basic density) resulted in a gain of 4.3% for DBH, 7.9% for BD and marginal changes for all other traits, with a net impact in profit of $1,270/ha. However, future profit calculations will need to consider the effect of FL, MFA and CC on the economics of wood processing to fully evaluate the economic impact of breeding.

Cellulose content as a selection trait in breeding for kraft pulp yield in Eucalyptus urophylla

“…However, estimated genetic correlations of cellulose content and wood density with growth traits in our study are in general agreement with previous studies in Eucalyptus species; these report a wide range of estimated genetic correlations, many of them nonsignificant (Apiolaza et al, 2005;Kien et al, 2008;Kube et al, 2001;Raymond and Schimleck, 2002;Wei and Borralho, 1997). The genetic correlations between wood density and growth in our study agreed well with those of Kien et al (2008) who found genetic correlations between wood density and growth traits to be in the range from 0.10 to 0.28 and nonsignificant.…”

“…Coefficients of additive genetic variation were similar in both studies. The coefficient of additive genetic variation estimated for cellulose content in our study was also similar to the value reported by Apiolaza et al (2005) from an unthinned progeny test of E. globulus in Australia.…”

“…Among these methods, the diethylene glycol dimethyl etherhydrochloric acid (diglyme-HCl) method developed by Wallis et al (1997) uses less toxic chemicals, can be undertaken in sealed bottles and allows multiple samples to be processed at the same time. Cellulose content determined by this method is strongly correlated with whole tree kraft pulp yield estimated for E. globulus and E. nitens, with correlation coefficients ranging from 0.82 to 0.91 (Apiolaza et al, 2005;Kube and Raymond, 2002;Wallis et al, 1996).…”

“…The somewhat higher standard deviation obtained for the estimate of pulp yield duplicates (0.68%, or about 1.4% of the mean) contributes to imprecision of the relationships between cellulose and pulp yield. Several recent studies evaluating cellulose content have used NIR (near infrared reflectance) prediction of cellulose, using calibrations developed from a sub-set of the samples that have been chemically analysed for cellulose (Raymond and Schimleck, 2002;Schimleck et al, 2004;Apiolaza et al, 2005). Such calibrations enable accurate prediction of cellulose content from NIR information in E. globulus and E. nitens (R 2 = 0.83−0.92) (Raymond and Schimleck, 2002;Schimleck et al, 2004).…”

“…These focus mainly on two temperate eucalypt species, E. globulus and E. nitens (Apiolaza et al, 2005;Kube et al, 2001;Raymond and Schimleck, 2002;Schimleck et al, 2004), and Populus deltoides (Olson et al, 1985). Narrow-sense heritability of cellulose content is reported to be high, ranging from 0.32 to 1 (Apiolaza et al, 2005;Kube et al, 2001;Raymond and Schimleck, 2002;Schimleck et al, 2004), but the coefficient of additive genetic variation in one study was low (3%) (Apiolaza et al, 2005). Genetic gain in cellulose content from selecting the top 5% of the population, in studies by Kube et al (2001) and Schimleck et al (2004), was about 3-4% of the original population mean, with little effect on growth or wood density.…”