GENETIC-VARIABILITY IN ELITE EUCALYPTUS PROVENANCES AND PROGENIES SELECTED FOR ARID ENVIRONMENTS IN HAWAII

The achievement of significantly increased biomass yield per unit area through genetic improvement of trees is a primary goal of short-rotat ion intensive-culture (SRIC) of Eucalyptus and other tropical hardwood s in Hawaii. Twelve entries of Eucalyptus selected for arid environmen ts in Hawaii were assessed for genetic variation using four isozyme sy stems involving six loci (Pgi-2, Pgm-1, Pgm-2, Mdh-2, 6Pgd-1, and 6Pgd -2). They included five open-pollinated (OP) progenies of E. globulus; three OP progenies of Eucalyptus hybrids (two E. grandis X E. urophyl la hybrids and one E. grandis X E. camaldulensis hybrid); and four pro venances (two E. grandis provenances and one provenance each of E. cam aldulensis and E. saligna). As indicated by mean number of alleles per locus and observed and expected levels of heterozygosity, the three O P progenies of hybrids were the most variable, followed by the four pr ovenances and the three OP progenies of E. globulus. The importance of managing genetic variation to avoid deleterious impacts of inbreeding in these elite Eucalyptus selections in a long-term tree improvement program for sustainable commercial SRIC plantations is discussed.