Recent advances in mass micropropagation of acacia species

Acacia species, and more especially Acacia mangium, have become major plantation tree species in Sabah and South-East Asia. These tree species are mostly used for pulp production. Due to the increasing demand of superior plant materials by local forest companies in Sabah, the Plant Biotechnology Laboratory has initiated micropropagation studies on three Acacia species : A. mangium, A. mangium x auriculformis hybrids and A. crassicarpa. The use of this tissue culture technology aims at cloning adult trees selected based on their growth performances in a shorter time than conventional methods of propagation such as production of cuttings. In the case of A. mangium 'x auriculiformis hybrids - that are known to have a better growth than the A, mangium pure parent species -vegetative propagation is the only mean of propagation since propagation by seeds from bi-specific orchards still remains not feasible at the present time. We recently developed successfull micropropagation methods and appropriate culture media on these three Acacia species. Our micropropagation experiments were mainly focused on the improvement of the multiplication rate and in vitro rooting ability. These protocols firstly developed on juvenile plant material (seedlings) were further applied to mature selected material. The in vitro introduction of shoots - directly collected on mature selected trees as well as further multiplication, rooting and ex vitro acclimatization in nursery of the produced plantlets were shown to be successful. Although micropropagation methods can theoretically produce an infinite number of plantlets, the combination of both in vitro and conventional methods of propagation will be the most cost-effective strategy to be applied for large-scale afforestation programs. (Résumé d'auteur)