Genetic variation in shrinkage properties of Eucalyptus pilularis assessed using increment cores and test blocks

Assessments of genetic variation in wood properties are difficult and expensive to carry out. As a consequence, the inclusion of wood quality traits in eucalypt breeding programs has to date been limited. This study is part of a large investigation into the use of non-destructive methods of assessing wood properties by comparing the results with traditional destructive methods. This component of the study investigates the genetic variation in linear shrinkage of 152 open-pollinated families of Eucalyptus pilularis (Smith). Increment cores and test blocks were used to assess radial and tangential shrinkage as well as their ratio. Shrinkage results at 17% MC, 12% MC and 5% MC are presented here. Heritability estimates were moderate for tangential shrinkage but not significant for radial shrinkage or the ratio of the two. The genetic correlation between shrinkage measured on cores and on blocks at this stage was not sufficient to justify the use of increment cores alone in genetic assessments. Basic density had a moderate and negative correlation with tangential shrinkage, suggesting that selecting for higher basic density may help reduce tangential shrinkage. The increment core method was not successful at measuring radial shrinkage due to core distortion but an improved method is suggested. Measurements from scans and blocks showed that radial shrinkage was not heritable.