Pears

Abstract

The most important commercial pear species grown are Pyrus communisand P. pyrifolia, although there are significant acreages of several other species. Climatic adaptation is a concern of all pear breeders, as well as fruit quality, season extension, compatibility with major pollenizer cultivars and disease resistance. Increasing fire blight resistance is an important goal in the eastern and southern parts of North America, and many regions of Europe. In the breeding of pear rootstocks, the common goal is to develop rootstocks that induce size control and precocity in the scion cultivar. Resistance to fire blight is quantitatively inherited in an additive fashion, with a few major genes playing an important role. Genes have also been identified for semidwarf or compact cultivars, short-internode dwarfs and short internode compact pears. Varying amounts are known about the genetics of fruit development and quality. Molecular studies have been conducted on the expression patterns of genes during fruit ripening and storage. Several genetic maps have been developed of pear and DNA markers have been linked to a number of resistance genes including black spot disease, scab and fire blight resistance. Transformation strategies have been employed to generate herbicide and disease resistant plants.