GENETIC PARAMETER ESTIMATES FOR PRODUCTION AND QUALITY TRAITS OF PINUS-ELLIOTTII ENGELM VAR ELLIOTTII IN ZIMBABWE

P. elliottii ENGELM. var. elliottii is an important exotic plantation species in Zimbabwe, where it is grown for saw-timber and resin produc tion. Two progeny tests, originating from factorial matings between pa rents selected in plantations, were assessed at 5, 8 and 15 years. Thi s paper reports genetic parameter estimates for important production a nd quality traits. All traits assessed were under a reasonable degree of additive genetic control, with the magnitudes of non-additive genet ic variances almost invariably somewhat less than those of additive ge netic variances. Narrow-sense heritabilities for growth traits, wood d ensity and resin yield were moderate to high, ranging from 0.16 to 0.4 2; those for stem straightness and branching traits were lower, rangin g between 0.04 and 0.17. Genetic correlations at each of the assessmen t ages were more variable; of most consequence for production were the slight negative correlations between wood density and both stem diame ter and volume, and the slight positive correlation between density an d height. Age-age correlations for growth traits were high, indicating potential for early selection. Age-age correlations for other traits were variable.