Performance differences among ex situ native-provenance collections of Pinus radiata D. Don. 1: potential for infusion into breeding populations in Australia and New Zealand

Growth and form traits from a series of three provenance trials of Pinus radiata D. Don planted in New Zealand and Australia were analysed at age 9 years from planting. The trials included selections from three mainland California natural populations—A?o Nuevo, Monterey and Cambria. Monterey and Cambria performed better than A?o Nuevo at two New Zealand sites, but Monterey and A?o Nuevo were almost identical in growth, whereas Cambria grew less vigorously at the Australian site. We detected significant provenance differences for diameter at breast height (DBH) growth and stem straightness across countries (p < 0.001). Estimated heritability for DBH ranged from 0.19 to 0.26 within sites, while heritability estimates for stem straightness and branching frequency ranged from 0.10 to 0.24. Estimated type B genetic correlations for DBH were always higher between the two trials in New Zealand trials than between pairs of trials in New Zealand and the Australian site. The genetic coefficient of variation (CV_A) for DBH was around 8–10% compared to ca. 5% for the current breeding population. These results suggested that there is appreciable genetic variation in the native populations, and infusion of these materials would increase the genetic variation in current breeding populations. Ten unrelated parents ranked above control seedlots from the older open-pollinated seed orchard stock for DBH growth and would be potential candidates for infusion. The promising performance of the Cambria material is an important result because the genetic base of the present Australian and New Zealand plantations is principally derived from A?o Nuevo and Monterey.