Genetic parameters for cold hardiness in Eucalyptus nitens (Deane & Maiden) Maiden

Provenance effects and genetic parameters for survival, growth, and frost damage aspects of cold hardiness in Eucalyptus nitens (Deane & Maiden) Maiden were estimated from almost 5,000 trees in two field tests established in 1984 and 1986. Significant and consistent differences amongst the six provenances were found for all cold hardiness traits. Macalister, Rubicon and Toorongo provenances from the central highlands of Victoria performed similarly and were always the best (overall survival 71%). Northern New South Wales (NSW) and Southern NSW were ranked next (overall survival 34%) and were often not significantly different from each other. Errinundra was the poorest (overall survival 13%). Northern NSW, whilst best on the basis of artificial freeze testing (T50, -8.4°C c.f -7.5°C overall average), appeared poorly adapted to survive and grow on either test site. Only the Macalister, Rubicon and Toorongo provenances were used for genetic parameter calculation (188 families and 3,500 trees). Individual tree narrow sense heritability (h 2) for basal area (BA) at about 6 years of age was lowest at the coldest site (h2 range 0.10-0.27), whilst for frost damage in the field (F88) at about 2-4 years of age it was highest at the coldest site, (h2 range 0.14-0.44). Separate T50 assessments appeared to measure a heritable trait (h2 = 0.29 and 0.96) and to be repeatable (r Bg = 0.86). However, there was apparently only a moderate relationship between T50 and F88 (average rBg = 0.39 and 0.29 for the two sites respectively). At the two sites F88 from the same autumn freeze event, was moderately correlated (rBg = 0.45). Strong negative genetic correlations existed between F88 and BA, indicating that high levels of frost damage are associated with poor growth and survival, as one might expect. Breeding values predicted using best linear prediction, indicated that the best families were about 1.4°C (19%) better for T50, 20 cm2 (20%) better for BA and had 11% less foliage damage (22% better) for F88. The findings are discussed in terms of the interaction between frost tolerance and growth conferring ability to survive and grow on very cold sites.