Achievements in forest tree genetic improvement in Australia and New Zealand. 5: Genetic improvement of Douglas-fir in New Zealand.

摘要

Douglas-fir (Pseudotsuga menziesii) is New Zealand's (NZ) second most important plantation species and has been grown there since the late 1800s. Recently there has been increased commercial interest in the species, especially for higher-altitude, snow-prone sites in the southern South Island. Tree improvement began in 1957 with the establishment of extensive large-plot provenance trials. These have shown that coastal fogbelt provenances from California and southern Oregon, USA, are superior in growth to those of Washington coastal origin. The Washington provenances had been used for much of the afforestation up to 1980. A first breeding programme, started in 1969 from stands of Washington origin, became redundant following the provenance trial findings and, in 1988, selection of 186 plus trees in provenance trial plots of coastal Californian and Oregon provenances restarted the breeding programme. In addition, open pollinated seed from 240 parents in 21 coastal Californian and Oregon populations was planted as a breeding population in 1994. An ambitious programme of polycrossing and paircrossing of NZ selections failed to deliver sufficient crosses and seed, and recently a new breeding strategy based on open pollination in a clonal archive of the 1988 selections has been instituted. The breeding objectives have also been recently revised to include volume yield, log quality and timber stiffness, selection criteria being diameter, bole straightness, light well-distributed branching and outerwood density and/or sound velocity..