The forest tree species of interest in the 11 SADC countries evaluated can be grouped into four broad groups namely industrial exotic plantation timber, indigenous timber species, indigenous fruit trees and agroforestry species. The tree improvement programmes for these species vary from simple species or provenance selection to complex programmes involving advanced breeding and selection methods, hybridisation and cloning. The most advanced evaluation programme is that of industrial exotic plantation tree species of pines and eucalypts, which are either private company or government initiatives.
The breeding programmes of indigenous fruit tree species and agroforestry tree species are largely simple evaluations of the different seed sources. These evaluation programmes are both individual and regional country initiatives (Maghembe et al., 1998; Shumba, 2001). The indigenous fruit tree species that have been evaluated include U. kirkiana, S. cocculoides, P. curatellifolia, S. birrea, A. garckeana, D. mespiliformis, and V. infausta. The agroforestry tree species that have been evaluated include A. erioloba, A. karoo, A. nilotica, A. senegal, A. tortilis, F. albida, Sesbania sesban, A. angustissima, C. calothyrsus, G. sepium, L. diversifolia, L. leucocephala, L. pallida and T. vogelli (Barnes, et al, 1999; Barnes, 2001).
The major objective of the improvement programme of industrial forest tree species is to improve the timber or pulp yield of the trees species and also tannin bark in the case of A. mearnsii. Gains of such breeding programmes have been estimated in South Africa and Zimbabwe to be in the region of between 10 and 38% in volume production, up to 5 years reduction in rotation age and 10% reduction in pruning costs due to reduced branch sizes. Development of interspecific hybrids of gums and their subsequent cloning increased timber yields by as much as 46%.
