Osmoregulators proline and glycine betaine counteract salinity stress in canola

Salt inundation leads to increased salinization of arable land in many arid and semi-arid regions. Until genetic solutions are found farmers and growers must either abandon salt-affected fields or use agronomic treatments that alleviate salt stress symptoms. Here, field experiments were carried out to study the effect of the osmoregulators proline at 200 mg L-1 and glycine betaine at 400 mg L-1 in counteracting the harmful effect of soil salinity stress on canola plants grown in Egypt. We assessed growth characteristics, yield and biochemical constituents. Results show first that all growth characters decreased with increasing salinity stress but applied osmoregulators alleviated these negative effects. Second, salinity stress decreased photosynthetic pigments, K and P contents, whilst increasing proline, soluble sugars, ascorbic acid, Na and Cl contents. Third, application of osmoregulators without salt stress increased photosynthetic pigments, proline, soluble sugars, N, K and P contents whilst decreasing Na and Cl contents. It is concluded that the exogenously applied osmoregulators glycine betaine and proline can fully or partially counteract the harmful effect of salinity stress on growth and yield of canola.© INRA and Springer-Verlag, France 2012

Breeding for salt tolerance in crop plants - the role of molecular biology

Salinity in soil affects about 7 % of the land's surface and about 5 % of cultivated land. Most importantly, about 20 % of irrigated land has suffered from secondary salinisation and 50 % of irrigation schemes are affected by salts. In many hotter, drier countries of the world salinity is a concern in their agriculture and could become a key issue. Consequently, the development of salt resistant crops is seen as an important area of research. Although there has been considerable research into the effects of salts on crop plants, there has not, unfortunately, been a commensurate release of salt tolerant cultivars of crop plants. The reason is likely to be the complex nature of the effect of salts on plants. Given the rapid increase in molecular biological techniques, a key question is whether such techniques can aid the development of salt resistance in plants. Physiological and biochemical research has shown that salt tolerance depends on a range of adaptations embracing; many aspects of a plant's physiology: one of these the compartmentation of ions. Introducing genes for compatible solutes, a key part of ion compartmentation, in salt-sensitive species is, conceptually, a simple way of enhancing tolerance. However, analysis of the few data available suggests the consequences of transformation are not straightforward. This is not unexpected for a multigenic trait where the hierarchy of various aspects of tolerance may differ between and within species. The experimental evaluation of the response of transgenic plants to stress does not always match, in quality, the molecular biology. We have advocated the use of physiological traits in breeding programmes as a process that can be undertaken at the present while more knowledge of the genetic basis of salt tolerance is obtained. The use of molecular biological techniques might aid plant breeders through the development of marker aided selection