Résumé
BEHAVIOUR OF THE "YSG BIOTECH TG1-8" TEAK CLONES UNDER VARIOUS SITE CONDITIONS: FIRST OBSERVATIONS
During the early 1990's in Sabah (East Malaysia), the Company Yayasan Sabah Group Biotech ("YSG Biotech"), jointly with CIRAD (France) Forest department scientists, has developed an efficient method for mass cloning superior teak trees, Tectona grandis, of any age by rooted cuttings and by micropropagation. The first clones were produced from eight superior ("Plus") trees initially selected on phenotypic traits and growth in Sabah under 2,500 mm/yr of rainfall without a distinct dry season. The outstanding field behaviour of the clonal offspring assessed locally rapidly led to their mass propagation to meet local and international demands. Since then, millions of clonal offspring have been produced from the eight "Plus" trees and the demands keep increasing due to the attractiveness of these materials. This context has prompted us to compile the information available on the field behaviour of these clones during their early stages of development in the different countries where they have been planted. The first observations indicated that the eight clones adapt surprisingly well to a wide range of environmental conditions, outperforming all other teak sources in terms of productivity and qualitative traits in every location where they had been planted. These include places with annual rainfall of 1,000 mm and eight months of dry season, which is in total contrast to the conditions of their selection in Sabah. Nonetheless, sites with high rainfall evenly distributed throughout the year are observed to be more suitable to guarantee the best true-to-type development of these clones. One of their main assets is the early and rapid production of a long and straight clear bole with minimal lateral branching which helps to alleviate costly silvicultural practices such as pruning, while encouraging their utilization in agro-forestry. The availability of these clonal materials has boosted large-scale establishment of clonal teak plantations in many tropical countries.