Basic density, diameter and radial variation of Vanuatu whitewood (Endospermum medullosum): potential for breeding in a low density, tropical hardwood. (Special Issue: Domesticating native tree species for development in small island nations.)

摘要

Vanuatu whitewood (Endospermum medullosum L.S. Smith) is an economically important timber species for Vanuatu. Inter- and intraprovenance genetic parameters for stem diameter at breast height, basic density and radial variation in density, were estimated for two provenances selected from a 12.4-year-old open-pollinated seed orchard on Espiritu Santo Island, Vanuatu. Kole provenance exhibited the highest mean basic density, greatest mean diameter and greatest radial variation in density across the stem. Mean basic density at breast height was 345+or-2 kg/m3. Growth rings were not visually discernable and colour was homogenous across all samples. For radial variation determination, each pith-bark core was sectioned into four equi-length subcores (A-D). Subcore density increased consistently and significantly from pith to bark, with mean basic density of 308+or-3, 327+or-3, 343+or-3 and 359+or-3 kg/m3 for cores A-D respectively. The narrow-sense heritability estimate (h2) was low (0.26+or-0.2) for diameter, with a moderate coefficient of additive genetic variation (CV_A=17.61%). Estimated h2 for density was moderate (0.49+or-0.24), with a low coefficient of additive genetic variation (CV_A=5.39%). Though the precision of these estimates is modest, reflective of the small sample size, indications are that the heritable genetic variation in both growth and quality traits will result in economic gain from a recurrent selection and breeding program.