Growth and form ofEucalyptus nitensprogenies in New South Wales, and selection strategies for a seedling seed orchard

Summary Eucalyptus nitens is potentially the most important eucalypt species for plantations in the tablelands regions of New South Wales. However, genetic parameters and data for provenance and progeny performance of the species in this State have previously not been available. A test of 30 open-pollinated families was established near Tumbarumba (NSW) in 1989, and assessed for a number of growth and form traits at age 5 years. Victorian provenance material, including seedling seed orchard progenies, was generally superior to NSW seed sources for growth and form traits but more prone to forking; all provenances included some superior individual families. Estimates of individual heritability were low to moderate (0.14 to 0.44) for seven growth, stem and branch form traits, with low standard errors, and very low for occurrence of forks and ramicorn branches. Genetic correlations among commercially important growth and form traits were generally moderate to high, and favourable. Selection of trees in the test to retain in a theoretical seedling seed orchard, using a multi-trait selection index, resulted in retention of 90 trees over 11 families, with high gains in growth and form (13.2 to 20.7 percent). Alternative selection strategies, retaining 90 trees over 15 families, gave somewhat lower gains in most traits but a more even distribution of trees over the orchard area.