Assessment of three-year DBH and height data and genetic gain prediction for five Acacia mearnsii (black wattle) subpopulations in South Africa using REML/BLUP

Abstract

Recent research has shown Acacia mearnsii (black wattle) to be a source of high-quality pulp. This led to a change in the emphasis in the breeding programme at the Institute for Commercial Forestry Research, from improving bark yield and quality, to improving timber yield and quality while maintaining an acceptable bark quality. A Multiple Population Breeding Strategy was implemented to cater for these changes. Six subpopulations were established across different sites in KwaZulu-Natal and were determined by origin of seed. Five of these subpopulations were established in 2002 and the sixth one in 2004. Each subpopulation was established as a progeny trial with a breeding seed orchard adjacent to it. The management of the seed orchards will be determined according to the performance of the families within the progeny trials. This paper is a summary of the three-year growth measurements taken from the first five subpopulations. The results showed promising heritability values with respect to genetic gain. These data were then projected to estimate results at full rotation using appropriate growth models. Results showed that if one selects the top 20 individuals, mean annual increments (MAIs) of 13.20–19.60m³ ha^–1 y^–1 can be expected. If one selects the top 20 families, MAIs of 10.60–19.10m³ ha^–1 y^–1 can be expected. Growth data will continue to be collected each year. This will allow for continuous assessment of age–age correlations for the various traits being assessed, and will provide an appropriate decision-making tool for selecting individuals for future generations.

Southern Hemisphere Forestry Journal 2007, 69(2): 111–116