Genetic parameters and correlations between stem size, forking, and flowering in teak (Tectona grandis)

The genetic improvement of teak (Tectona grandis Linn. f.), a high value tropical hardwood, has been hindered by a paucity of genetic parameter estimates. In particular, an association between flowering age and forking height has been suggested but never before quantified. In this study, 3- to 6-year data from a cloned progeny test were used to estimate heritability and genetic correlations among stem size, forking, and flowering traits. Mean narrow-sense heritability estimates ((h(2)) over cap) were 0.09-0.10, and mean broad-sense heritability estimates ((H-2) over cap) were 0.38-0.45 for stem size traits. There were no age trends in (h(2)) over cap or (H-2) over cap. Age-age additive and nonadditive genetic correlations were strong and were not related to the time interval between measurements. Forking height and forking age were under weak to moderate genetic control. Flowering age was under substantially greater genetic control, with (h(2)) over cap of 0.21 and (H-2) over cap of 0.46. Additive and nonadditive genetic correlations between forking height and flowering age were estimated to be 0.84 and 0.55, respectively. Improvement of forking height was calculated to be almost twice as efficient by indirect selection on late flowering. These results suggest that within-provenance selection for teak stem size need not be delayed beyond 3 years and that indirect selection on flowering age will improve forking height.