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For many years most tree improvement programs included growth, form, adaptability, and pest resistance in their assessments but did not include wood properties as such. It was recognized that tree form, growth rate, and pest tolerance could all affect wood in several ways, as was described by Zobel (1971) (Fig. 1.1). However, the potential for improving wood by direct application of genetics was not generally appreciated, although persons like Harris (1983) strongly emphasized the value of employing genetics to improve wood. Many people felt that if growth, form, and adaptability were central to a genetics program, there would be little opportunity left for altering wood, even if there were strong genetic control. However, as noted by Zobel (1972): “Addition of a wood property will enable moderate changes in wood while still being able to maintain the desired form, growth, and adaptability.” As early as 1935, Schreiner recognized the possibilities for genetic manipulation of wood and published an article on how pulping characteristics might be improved by breeding; these ideas were later expanded in his 1958 paper. The economic impact of changes in wood quality were recently outlined by Cubbage (1990). However, little proof was available regarding the inheritance of wood properties except for studies like those of Pawsey (1965) in Australia, who tested the wood of clones of radiata pine (Pinus radiata) and found large differences among clones but great similarity among ramets within a clone. The general possibility of improving wood quality through breeding was covered by Lahiri (1959) and an assessment of the wood qualities to use in tree breeding was made by Dadswell et al. (1963) in Pinus radiata and for Douglas-fir (Pseudotsuga menziesii) by Kellogg (1990). |
