Natural variation in shining gum, Eucalyptus nitens.  II. Second progress report.  L. A. Pederick.  February 1985.  33 pp. (unpubl.)

SUMMARY

This second report on genetic variation in Eucalyptus nitens (Maiden) (shining gum) presents progress results on a series of trials that includes a small pilot trial planted in 1968 and three major trials planted in 1972, 1975 and 1978.

The results confirm the previously reported evidence of the existence of two main forms of the species, namely:

1. a faster growing juvenile-persistent-foliaged form, occurring naturally in the Central Highlands of Victoria (Rubicon, Toorongo and Macalister provenances) and in both southern and northern N.S.W.; and
2. a slower growing early-adult-foliaged form, occurring naturally on the Errinundra Plateau.

However, trees with characteristics similar to those of the Errinundra provenance were found in that portion of the Central Highlands designated as Toorongo provenance. Although most stands in this area were of the juvenile-persistent form, populations of trees with a blend of the two forms were found on the south-west slopes of the Baw Baw Ranges. The Errinundra characteristics were pronounced in trees derived from Christmas Creek and less so in trees from Tanjil Bren and Mt Toorongo to the north¬west. This evidence was taken to indicate that gene flow of the Errinundra-type characters had taken place in that direction, though no gene flow appears to have taken place to the east of Christmas Creek, where the nearest stand sampled (Mt Erica, 5 km away) exhibited only the characters of the juvenile-persistent form, normally typical of the Central Highlands.

The faster growth rate of the juvenile-persistent form was still exhibited in the oldest trials available - 12 years of age. On the other hand, trees of Errinundra provenance had thinner branches. Therefore, although the Central Highlands provenances are recommended over the Errinundra provenance for use in forest operations on suitable sites because of their faster growth rate, the branch characteristics of the Central Highlands provenances should be capable of some improvement by breeding. The N.S.W. provenances were inferior to those of the Central Highlands in both growth and form.

Of the Central Highlands provenances, Toorongo and Macalister had straighter stems than Rubicon, and Toorongo had better (thinner) branches than Rubicon or Macalister. Trees of Mt Wellington (Macalister) seed origin had the coarsest branches in the Central Highland's group of provenances. Toorongo (juvenile-persistent form) was rated the best on the basis of both growth rate and tree form. Of the localities sampled within that provenance, St Gwinear and Mt Erica appeared to be the best, though not significantly better than the other Toorongo localities with the juvenile-persistent form.

There was considerable variation between families of the Central Highlands provenances in the trials, with some of the Rubicon and Macalister families being as good as the better Toorongo families for both growth and form. Therefore, for purposes of developing an improved breed of shining gum for Victorian forest plantings, a breeding population could be composed of selections of Rubicon and Macalister as well as Toorongo provenances, though the latter should predominate, particularly selections originating in the St Gwinear and Mt Erica stands. The best trees in the better families of the three major trials, particularly that of 1978, would be suitable as a basis for selection and propagation of such a breeding population.

The option of growing trees of the best Central Highlands provenances on the Errinundra Plateau is discussed.