BREEDING FOR DISEASE RESISTANCE IN FOREST TREES

Breeding for disease resistance in forest trees is a specialized kind of forest tree breeding. With breeding of white pines for resistance to blister rust as an example, the various problems encountered and solved are described. Resistance to blister rust in eastern white pine has thus far been found to be inherited on a polygenic basis. This influences the choice of effective breeding methods and the silvicultural use of the resistant materials obtained. The genetic basis of superior resistance found in exotic species, such as Balkan white pine, Japanese white pine and Himalayan white pine is also influencing the breeding methods. Because of its early flowering, breeding work with Balkan white pine has progressed further than with other exotic species. Indications have been obtained that resistance in this species is also based on polygenes. Some of these are complementary to those found in eastern white pine. In Himalayan white pine materials the presence of recessive major genes for resistance as well as polygenes is probable. The possible use of these findings in the development of resistant white pine materials and their use in the establishment of artificially and naturally regenerated stands is discussed.