Tree Breeding

Abstract

Tree breeding involves mating parents with desirable traits to produce more desirable offspring. Many different traits can be modified through breeding including growth vigour, resistance to pests or diseases or wood quality. Tree breeding is based on the principles of plant genetics and these are described briefly. Over many generations of a breeding programme, a ‘breeding population’ of individual trees displaying desirable traits is identified. These trees are interbred in complex ‘mating designs’ devised by highly skilled quantitative geneticists to maximise the chances of obtaining offspring that show substantial gains in the desired traits. The matings are often carried out in seed orchards from which seed is obtained for the next generation of the plantation programme. As well, large numbers of cloned seedlings of a highly desirable individual may be produced using various propagation techniques, including cuttings, air-layering or tissue culture. Genetic engineering, the artificial manipulation of the genes that a plant contains, is becoming an important additional part of tree breeding programmes. Genetically engineered traits being considered in various tree species are resistance to disease and insect attack, desirable branching characteristics, growth rate, flowering behaviour, improved wood quality, reduced foliage digestibility to pests and tolerance to weedicides, soil pollution or cold.