A plan for the breeding of radiata pine in the Department of Conservation, Forests and Lands.  L. A. Pederick.  June 1987.  50pp. (unpubl.)

SUMMARY

The report commences with an outline of achievements in the Department's radiata pine breeding program and a discussion of factors influencing the development and choice of techniques. A plan of action is outlined for the future.

The program commenced in 1958 when 28 'plus trees' were selected in state plantations to be used as breeding stock. They were vegetatively propagated by grafting to form clones. The number of first generation clones has been gradually increased by further selection and by exchange with tree breeders elsewhere in Australia and New Zealand to the present number of 164. A special nursery has been established at Creswick and grafts of each clone established in a breeding arboretum nearby for convenient production of scions for grafting and of flowers and pollen for use in controlled pollination.

Progeny trials, with open-pollinated and control-pollinated offspring, have been established almost annually for the purpose of determining the breeding value of the clones. Later, in these trials, the best individual trees in the best families have been selected and cloned to be used in a second generation of breeding which should yield greater improvement than the first.

Seed orchards established at three sites, Korweinguboora, Lal Lal, and Campaspe, during 1961¬1972, with the best clones then available, have been harvested annually for improved seeds for operational use since 1970. Gains in volume growth of trees grown from orchard seeds have been estimated as 7.4%, which was increased to about 10% when the poorest clones were cut out of the orchards. The Campaspe orchard was destroyed by fire in 1983. As a result, the Department is not yet able to achieve regular production of its full requirement of seed. Though the Campaspe orchard has been replanted with an improved selection of clones, a further large new orchard is needed for the Department to meet its seed requirement in the years ahead as well as to achieve the higher gains obtainable from the better clones now available.

The report contains details of the various aspects of breeding and includes information on the clones in the breeding populations, progeny trials and annual yields of seeds from the orchards.

It is proposed that breeding work should be continued, because of indications that further substantial gains are obtainable.

A plan has been prepared which aims at progressive improvement of the species on a statewide basis through accumulation of good genes over a number of generations. Each generation involves controlled cross pollination among selected clones according to a mating design (4 x 4 factorial design preferred) to create families to be tested in progeny trials. Following a full assessment of each trial at age 8-9 years, the most outstanding individuals (in the best families) will be selected, grafted and planted in the breeding arboretum for use in the next generation. Generation cycle length will be 16-19 years.

Four traits will be improved by breeding - growth rate, stem straightness, branch thickness (fine) and wood density (high). The clones in the breeding population will be divided into sublines (groups) and breeding restricted to the clones within each subline. The purpose of sublines (which will be unrelated to each other) is to facilitate the selection of unrelated clones to be used in future seed orchards, in order to avoid depression of gains due to inbreeding effects. The number of sublines should be about the same as years in the generation cycle, and the sublines be formed into a series of annual age classes so that the workload can be spread evenly over a breeding generation. Selection of new clones to increase the breeding population is desirable.

This breeding plan will result in gradual improvements. Options for increasing the gains further include:

1. Restriction of seed collection to a small (and superior) proportion of the clones in the orchards.
2. Production of superior seeds by controlled pollination of crosses known to give high yields.
3. Large scale propagation of improved genotypes by cuttings.

The potential exists to achieve large increases in tree yields and quality by combination of (2) and (3), but (1) not be possible until the Department develops a nursery in which to grow cuttings on a large scale. The use of cuttings is particularly appropriate for mass production of genotypes found to be adapted to atypical sites, e.g. the fertile farm sites of northeast Victoria.