Genetic characterisation of a Eucalyptus nitens base breeding population in South Africa

Abstract

The measurement and statistical analysis of data from eight Eucalyptus nitens trials established in the summer rainfall forestry region of South Africa during the 1980s and 1990s, have enabled the characterisation of the Institute for Commercial Forestry's breeding population. Provenance testing showed that the more northerly New South Wales (Australia) Eucalyptus nitens provenances of Barren Mountain and Barrington Tops are distinctly better suited to the summer rainfall areas of South Africa than the southern New South Wales provenances and the Victorian provenance, Penny Saddle.Generally, the species was not badly affected by Coniothyrium canker. High Type B genetic correlations for all sites pairs, except one comparison, ranged from 0.75 to 0.99 for dbh, indicating very little, or no, genotype-environment interaction for diameter at 1 breast height for the genotypes tested in this study. Narrow sense heritability coefficients ranged from 0.01 to 0.34, indicating that the species generally exhibits sufficient breeding opportunity for improvement of diameter growth. High genetic correlations of greater than 0.90 between diameter measurements at 52 to 62 months after establishment and diameter measurements at 94 or 113 months were found, indicating that selections can be reliably made at five or six years.Predicted genetic gains were highest in the trials at Goedehoop and Arthur's Seat, with increases in diameter at breast height of 3.07 cm (17.1%) and 3.17 cm (20.7%), respectively, at full rotation.

An investigation of assumptions made in estimating genetic parameters and predicting genetic gain in a Eucalyptus nitens breeding programme in South Africa

“…Details of these F1 trials, statistical analysis thereof, estimation of genetic parameters for the F1 and predicted gain for the F2 can be found in Swain et al (2013b). Both the estimation of genetic parameters in the F1 and predicted gains for the F2 used a coefficient of relationship of 0.33 (Swain et al 2013b).…”

“…Details of these F1 trials, statistical analysis thereof, estimation of genetic parameters for the F1 and predicted gain for the F2 can be found in Swain et al (2013b). Both the estimation of genetic parameters in the F1 and predicted gains for the F2 used a coefficient of relationship of 0.33 (Swain et al 2013b). These trials were subsequently thinned to seed orchards, based on the results of the final measurements, and seed collected over several years to establish progeny trials (F2) of this material (Swain 2013).…”

“…The authors also investigated the effect of provenance in variance component estimation, i.e., families nested within provenance (family (provenance)) and families across provenances (Swain et al 2013b), but as this and other studies have shown that across-provenance estimates result in overestimates of additive genetic variance (Brawner and Elizaul 2007;Johnson 1996;Tibbits and Hodge 1998), this scenario was not included in this report. The scenarios investigated were: 1) Coefficient of relationship and outcrossingFollowing the approach of Squillace (1974), and extending his calculations, it has been shown that 30% selfing gives an average coefficient of relationship among open-pollinated (OP) progeny of 0.4 (Griffin and Cotterill 1988) and 25% selfing gives an average coefficient of relationship of 0.5 (Hodge et al 1996).…”

“…Recently, similar studies have been done on stand volume in E. globulus (Callister et al 2013), and on E. cladocalyx, incorporating molecular markers to calculate inbreeding rates and coefficients of relationship (Bush et al 2011). This study will also indicate whether there are important digressions from the assumptions made in the F1 study (Swain et al 2013b), and whether the E. nitens breeding strategy needs to be adapted to take these into account.…”

“…juvenile-mature and trait-trait genetic correlations, as well as an indication of the presence/absence of genotype by environment interaction (Swain 2013;Swain et al 2013b).These have been invaluable in determining the breeding potential of the E. nitens population, selection of superior families and individuals, as well as informing the breeding strategy for the species. Genetic gain trials allowed for comparison of realised gain in the F2 with predicted genetic gain from the F1 (Swain 2013), and this provides an opportunity to assess the performance of the quantitative predictions using our underlying assumptions in the F1.…”