Apple

The cultivated apple, Malus xdomestica Borkh., is a interspecific hybrid complex of allopolyploid origin. The progenitor species is thought to be M. sieversii (Lodeb.) Roem., which hybridized with both European and Asian species throughout its domestication. Modern breeding continues to employ relatively few of the 25-30 species of Malus from throughout the northern hemisphere for both scion and rootstock development. The apple is the most produced temperate tree crop and is widely grown throughout the temperate zone and recently it has been expanding into subtropical and tropical zones. Major goals of scion breeding programs include fruit quality, disease resistance (scab, fire blight, powdery mildew), nutritional components and excellent postharvest traits to allow long storage and use as a fresh-cut product. Rootstock breeding efforts emphasize resistance to abiotic and biotic stress as well as plant vigor control. Much progress has been seen in the integration of biotechnology with the development of transformation systems, multiple maps, a large number of markers, extensive EST libraries and, most recently, with the whole genome sequencing of apple. Research has identified marker-traits associations for various disease resistance, plant architecture, postharvest, and flavor traits. International collaborative efforts are actively working to exploit the biotechnological approaches to understand the genetic basis of a range of commercially important traits to improve the efficiency of breeding programs.