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 Research’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 site pairs, except one comparison, ranged from 0.75 to 0.99 for diameter at breast
height (dbh), indicating very little or no genotype environment interaction for dbh for the genotypes tested in this
study. Narrow-sense heritability coefficients ranged from 0.01 to 0.34, indicating that the species generally exhibited
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 dbh of 3.07 cm (17.1%) and 3.17 cm (20.7%),
respectively, at full rotation.
