Breeding for Salt Resistance

Breeding for salt resistance was not very successful in the past. Major reasons are the multigenic character of salt resistance, a lack of pressure to breed for salt resistance in developed countries (in contrast to developing countries), and a lack of physiological knowledge. By combining strategies of salt resistance using conventional breeding methods based on a three-phase model of crop response to salt stress, it was possible to increase the salt resistance of maize. The newly developed hybrids were superior to the parent hybrid under semi-arid field conditions in Pakistan. This proof of concept revealed that Na+ exclusion at the root surface and from the shoot, Na+ inclusion in vacuoles, increase in H+ ATPase activity to increase leaf elongation and sink activity were major (but not exclusive) traits to improve the salt resistance. Interspecific hybridization to introduce Na+ transporters from a wild relative of wheat proved to be another successful strategy. Based on profound physiological knowledge it will be possible in the future to increase the salt resistance of existing high-yielding cultivars. The introduction of key salt-resistance genes using modern methods of biotechnology can help to accelerate pyramiding the strategies of salt resistance.