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Fifteen clones of teak (Tectona grandis) produced by micropropagation from 0.5 to more than 60 yr-old selected ortets were established in a clonal test in Sabah (East Malaysia) under 2500 mm of annual rainfall to compare their growth performances during the first 7 years of development. Field establishment was good with average mortality less than 10%. The clones developed rapidly true-to-type with significant between-clone differences in growth. Ranges of clone means were 13.6 to 19.3 m in height, 16.3 to 23.4 cm in diameter at breast height (DBH) and 129 to 264 dm3 in volume. Broad sense heritability estimates for these growth traits were lower overall for single trees (H2i) than for clone means (H2c) (H2i ≤ 0.257 vs H2c ≤ 0.634 for height, H2i ≤ 0.120 vs H2c ≤ 0.383 for DBH and H2i ≤ 0.125 vs H2c ≤ 0.364 for volume). The highest genetic gain that could be expected from the best three clones out of the fifteen compared was at age 2 for height (+0.66 m, or +11.7%), and age 3 for DBH (+0.87cm, or +10.4%) and volume (+4.65 dm3, or +15.7%). Age-related phenotypic correlation values were reliably (P < 0.0001) higher and more consistent for DBH (rP ≥ 0.61) than for height (0.37 ≤ rP ≤ 0.69), or than between DBH and height, except for height at 3 (0.51 ≤ rP ≤ 0.63) and 6 (0.55 ≤ rP ≤ 0.69) years. Height and DBH were moderately to highly genetically correlated (0.54 ≤ rG ≤ 0.90).

In the context of an increasing utilization of the interspecific hybrid Acacia mangium ؋ A. auriculiformis as a plantation tree in the tropical humid zone, its symbiotic characterization was carried out in comparison with that of its two parental species. Rhizobium strains of diverse geographical origins were isolated from root nodules of the hybrid and its parents. Almost all Acacia hybrid isolates were fast growing on yeast extractmannitol medium, in contrast to those isolated from both parental species, which were mostly slow growing. The rhizobium strains were characterized through partial sequencing of the rRNA operon. In the phylogenetic tree, almost all strains isolated from the hybrid were grouped together in a clade close to Bradyrhizobium japonicum, while all strains isolated from both parental species were close to Bradyrhizobium elkanii. Inoculation experiments performed under in vitro or greenhouse conditions showed that all strains were infective with their original hosts but exhibited very variable degrees of effectivity according to the host plant tested. Thus, homologous strain-host associations were more effective than heterologous ones. This shows that there is still a high potential for isolating and testing new strains from hybrids to be used as inoculants in the context of large-scale afforestation programs.

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Plantation-grown, high-value timber species producing high-value end products are key to optimising land utilisation in Sabah and Sarawak states in Borneo, Malaysia, while meeting the demand for downstream processing. Eucalyptus pellita is one such species suitable for the tropical climatic conditions and exhibits considerable potential for solid wood and veneer production. The characteristics of E. pellita grown in Sabah, demonstrate the need for an appropriate silviculture management and downstream processing strategy to optimise the quality and quantity of veneer and sawn board. Recovery from E. pellita resources has demonstrated the average volume recovery of dry-graded veneer ranged from 38.1 to 49.5%, whereas the average dried board volume ranged from 48.5 to 57.9%. If E. pellita is to be grown on short rotations as a peeler resource, an appropriate pruning regime is needed to maximise the volume of clearwood. The greatest cause of volume loss was end-splitting in the recovery of veneer and solid timber.