Abstract
A total of 1226 increment cores were sampled from two provenance trials of Pinus radiata D. Don planted in New Zealand (Kaingaroa) and Australia (Kangaroovale), to study variation and inheritance of wood density in selections from three mainland California natural populations: Año Nuevo, Monterey and Cambria. The study represents a back-to-back comparison of the same provenance and family material on contrasting sites between New Zealand and Australia. Monterey was significantly different to Año Nuevo and Cambria at Kaingaroa (p<0.05), and had slightly higher density, whereas all provenances were almost identical and not significantly different at Kangaroovale. However, there were significant differences for wood density at family level for Año Nuevo and Cambria at Kangaroovale. No significant provenance or family differences were detected for core length at either site. The estimates of heritability for wood density were all above 0.50 and generally higher at Kaingaroa than at Kangaroovale. Estimates of additive genetic correlations between wood density and core length were imprecise. Genotype × site interactions for density appeared minor (estimated type-B genetic correlation= 0.70) despite substantial differences in rainfall and soils. The similarity of Cambria to Año Nuevo for density is an interesting result because the genetic base of the present Australian and New Zealand plantations has been shown to be from Año Nuevo and Monterey. Infusion of Cambria material would increase the overall genetic base of the radiata pine breeding programs, with potential long-term benefits, despite the often disappointing growth performance of material collected from Cambria.