Genetics of shrinkage in juvenile trees of radiata pine from two test sites in Australia
Gapare, W. J.; Ivković, M.; Powell, M. B.; McRae, T. A.; Wu, Harry
To examine the genetic control of wood shrinkage(radial, tangential and longitudinal) in juvenile wood ofradiata pine (Pinus radiataD. Don), we assessed sam-ples collected at breast height in two related progenytests of age 8 and 9 years, established at two differentsites in Australia. Green to oven-dry tangential andradial shrinkage for the outer-rings was similar at bothsites. Similarly, mean longitudinal shrinkage for theouter-rings was similar at both sites (0.3 %, rangingfrom 0.1 to 1.9 at Flynn and 0.4 %, ranging from 0.02 to1.6, at Kromelite). Mean longitudinal shrinkage for theinner-rings was 4 times greater than that of the outer-rings at both sites. The magnitude of the gradient of lon-gitudinal shrinkage from pith to bark (0.001 to 2.9 %) islarge enough to cause distortion problems includingtwist and warp, during drying of sawn boards. Thesevalues also suggest that shrinkage in the juvenile coreof radiata pine is of major economic importance andtherefore should be improved either through genetics orsilviculture.Individual-tree narrow-sense individual heritabilityfor tangential and radial shrinkage in the outer-rings(4–6) was moderate at Flynn (0.24 ± 0.09 and 0.26 ± 0.07,respectively). There was a lack of significant geneticvariation for longitudinal shrinkage in the outer-ringsbut significant genetic control for the inner-rings (1–2)(h2= 0.26 ± 0.07). More samples per family are requiredto detect significant genetic variation for shrinkagetraits than other traits due to higher background varia-tion in sampling and measuring shrinkage traits rela-tive to other wood quality traits such as density,microfibril angle (MfA), spiral grain and modulus ofelasticity (MoE).
Pinus radiata; juvenile wood; distortion; shrinkage; genetic control
2008, Volym: 57, nummer: 3, sidor: 145-151
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