Selection indices for the genetic improvement of Caribbean pine to increase sawn timber production

Summary

Four selection indices were developed for Pinus caribaea Morelet var. hondurensis Barrett and Golfari grown in Queensland, in order to maximise the rate of genetic improvement in the volume of sawn timber recovered from 20-year-old trees. The first index placed no restriction on correlated genetic changes in density or spiral grain while the other three restricted changes in either or both of these wood properties to zero. Measurements of diameter at breast height, height and stem straightness made at 11 years were used as the controlling characters. For all indices, genetic responses in sawn-timber production were predicted using both mass selection and combined selection. Genetic gains of up to 18% were predicted, with an associated reduction of 13% in density. Gains in sawn-timber production of 8% were predicted with no decreases in density or spiral grain. Thus, substantial gains in sawn-timber production may only be possible at the expense of density. Other approaches for the development of a suitable selection index to improve sawn-timber production are discussed.