THE GENETIC-CONTROL OF FLOWERING PRECOCITY IN EUCALYPTUS-GLOBULUS SSP. GLOBULUS

The genetic control of flowering precocity was examined in 4 base popu lation trials of Eucalyptus globulus ssp. globulus in Tasmania, which include nearly 600 open-pollinated families from 46 collection localit ies. Flowering precocity (measured as the presence/absence of capsules and or flower buds at age 4) was found to be highly heritable (h(L)(2 ) = 0.47 or 0.59; averaged across 3 or 4 trials respectively), and exh ibit little genotype by environment interaction. Significant differenc es in the propensity for flowering precocity were observed between the 4 trials and also between different collecting localities. Progenies from localities on the Furneaux Group of islands showed significantly earlier flowering than those from other localities. Flowering precocit y was generally not genetically correlated with growth (average r(g) = 0.04), indicating that selection for this trait alone would have litt le impact on early growth. In addition precocious flowering was not si gnificantly correlated with pilodyn penetration (average r(g) = -0.07) , although the consistent negative genetic correlation across 4 trials may be indicative of a weak positive genetic relationship with wood d ensity. The potential of selecting for precocious flowering as a means of decreasing the generation interval in breeding programs is discuss ed.