Biotechnological advances in the genetic improvement of Prunus domestica
Résumé
Plum producers world-wide are facing multiple challenges including climate change, reductions in available labor, the need for reduced chemical inputs, the spread of native and exotic pests and pathogens, and consumer demands for improved fruit quality and health benefits. Meeting these challenges will require innovation in many areas of science and technology and especially in plum breeding. In an effort to develop new approaches to plum improvement the USDA-ARS Appalachian Fruit Research Station fruit breeding program in collaboration with partners in the U. S. and Europe have developed a genetic engineering (GE) approach to target resistance to Plum pox virus (PPV) the causal agent of sharka, one of the most destructive diseases of plum. This program has resulted in the development of a GE plum cultivar 'HoneySweet' which has been tested for 15 years in the European Union and in the U. S. and is highly resistant to PPV. 'HoneySweet' has received full regulatory approval in the U. S. 'HoneySweet' represents a new source of PPV resistance for growers and it can be used by breeders to develop additional resistant cultivars and/or rootstocks. Rapidly incorporating important traits into improved plum cultivars requires new approaches to breeding that can reduce or eliminate breeding limitations such as long juvenility periods; the need for extensive and costly breeding plots; and yearly limitations on flowering and fruiting related to seasonal dormancy. To address these limitations the USDA group and partners in the U. S. have developed a system to shorten the breeding cycle of plum. We have overcome the juvenility and environmental limitations of flowering and fruiting by incorporating a gene that induces trees to flower early and continually. We have reduced the plum generation cycle from 3-7 years to less than one year. We call this rapid breeding system "FasTrack". The system allows for the rapid incorporation of important traits into plums and then in the final generation, when substantial improvements are clearly evident, only seedlings that do not contain the early flowering transgene are selected. The selected trees may then be used directly as new cultivars, or improved lines for further breeding. Genetic engineering of important traits, FasTrack breeding, and other approaches that are under development will allow the latest advances in biology to be applied to improving and sustaining plum production.