Decay resistance of Scots pine wood
Anni Harju and Martti Venäläinen
Finnish Forest Research Institute, Punkaharju Research Station
Summary
The heartwood of old-growth Scots pine (Pinus sylvestris L.) has been traditionally
used in structures exposed to a risk of decay. Present-day timber from managed
forests comes from younger trees having a relatively low proportion of heartwood.
For evaluating the possibilities to increase the quality and the proportion of
heartwood by the methods of tree breeding, knowledge of genetic parameters is
needed.
We estimated the genetic parameters for the decay resistance of Scots pine sapwood
and juvenile heartwood. The wood material was obtained from two about 30-year-old
half-sib progeny tests and from a clone archive. Increment core samples were decayed
for 6 weeks in vitro using a brown-rot fungus Coniophora puteana as the test
organism (a modification of a standardised EN 113 method). The weight loss of the
wood samples was used as an inverse measure of the decay resistance.
The most marked feature describing the weight loss distribution was the considerably
wider phenotypic variation in the heartwood samples compared to the sapwood. The
proportions of the variance components differed greatly between the two progeny
tests. At the Kerimäki progeny test, the additive genetic component for the weight
loss of sapwood and heartwood was small compared to the total phenotypic variance,
which resulted in negligible narrow-sense heritabilities. At the Korpilahti progeny
test, where heartwood only was sampled, the narrow-sense heritability and the
coefficient of additive genetic variation indicated that it would be possible to improve
the decay resistance of Scots pine heartwood by direct selection. Offspring-parent
regression showed a moderate genetic determination of the heartwood decay
resistance. However, decay resistance as such is a complicated combination of traits
that are poorly known. In order to carry out the phenotypic selection successfully,
and especially to manage the stands to produce durable wood, the role of
environmental factors in the mechanisms associated with the passive decay resistance
of heartwood should be elucidated.
Nordic Group for Management of Genetic Resources of Trees
March 23-27, 2001
Meeting
in
Finland,