Abstract
Teak is one of most widely planted species in the tropics due to its high wood value. Two main questions motivated this research, how early can be performed genetic selection? and which is the optimal age selection in clonal Tectona grandis? A clonal test was established at northern Pacific of Costa Rica with 32 clones. Measurements were taken at ages 3.2, 3.6, 4.4, 4.9, 5.9, 8.9, 9.7, 10.6, 11.8, and 12.9 years old for diameter at breast height (DBH), commercial height (estimated), tree quality (assessed) and commercial volume. Genetic parameters and genetic correlations across ages for all variables were obtained through SELEGEN software (REML/BLUP). Individual DBH clonal heritability (H2gi) ranged from 0.02 to 0.11, while clonal mean heritability (H2mc) ranged from 0.43 to 0.82. Highest mean clonal heritability for commercial volume was registered between 8,9 and 9.7 years (H2mc=0,74 and 0,77), thus 8,9 became as the target selection age. Significant genetic correlations were found (rg=0.74) between DBH at 4.9 years and commercial volume at 8.9 years. Spearman rank correlation and graphical analysis determined high clonal DBH ranking stability after 4.9 years. Maximum selection efficiency for commercial volume was registered at age 5. Therefore, 9 years-old can be defined as the target age for selection in clonal teak, while early selection can be practiced under low risk through DBH ranking at 5 years, supported by an age-age genetic correlation of rg=0.74. Graphical analysis of ranking splitted in thirds proved to be an effective method to verify ranking stability across ages.