HOT-WATER EXTRACT AND PULP YIELD IN PROVENANCES OF EUCALYPTUS-REGNANS

Selection for pulp yield in a tree breeding program requires the pulpi ng of samples from large numbers of trees. Since pulping tests are ver y costly the use of hot water extract content as an indicator of pulp yield has been investigated for 11 year old Eucalyptus regnans. Hot wa ter extract was determined for samples taken at 1.3 m above ground fro m each of 10 trees from three provenances growing on two sites in Tasm ania. Twenty of these trees were individually kraft pulped. Composite samples of each provenance from each site were also pulped. The mean v alues for hot water water extract ranged from 2.9 to 3,9% and pulp yie ld for the composite samples from 52 to 53%. The degree of variation b etween trees within a provenance was much greater than the differences between provenance means for both extract content and pulp yield. For the 20 trees individually pulped the hot water extract was poorly and negatively correlated with pulp yield (r = -0.269). Hot water extract of breast height samples could not be used to rank genotypes for pulp yield and is therefore not recommended as an indirect selection crite rion.