Growth differences and genetic parameter estimates of 15 teak (Tectona grandis L.f.) genotypes of various ages clonally propagated by microcuttings and planted under humid tropical conditions

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 (r_P ≥ 0.61) than for height (0.37 ≤ r_P ≤ 0.69), or than between DBH and height, except for height at 3 (0.51 ≤ r_P ≤ 0.63) and 6 (0.55 ≤ r_P ≤ 0.69) years. Height and DBH were moderately to highly genetically correlated (0.54 ≤ r_G ≤ 0.90).