Enhancing drought and salinity tolerance in wheat crop grown in the Mediterranean region.

Drought and salinity are major constraints on crop production and food security, and adversely affect entire countries over several years resulting in serious social, economic, and environmental costs. Water is in an extremely short supply in up to 10 eastern and southern Mediterranean countries. Wheat production in the Mediterranean region is limited mainly by the availability of water resources. Investigating the mechanisms by which wheat physiologically adapts to water deficits points to a salinity tolerance strategy showed that varieties of wheat which are able to maintain photosynthesis and growth at low soil Ψw often display a relatively greater capacity for leaf osmotic adjustment. Understanding the molecular basis of salt-stress signaling and tolerance mechanisms in wheat is required for engineering local wheat genotypes more tolerant to salt stress. This goal can be achieved only by first deciphering the physiological responses of wheat to salt stress. Recent work at the molecular level has led to the identification and cloning of cDNAs encoding proteins which are involved in the cellular-level physiological system which facilitates this adaptive response. Transgenic Arabidopsis plants over-expressing wheat candidate genes encoding ion transport proteins (TNHX1, SOS1, TVP1), or dehydrin (DHN-5) are much more resistant to high concentrations of NaCl and to water deprivation than the wild-type strains. Over-expression of the isolated genes from wheat in Arabidopsis thaliana plants is worthwhile to elucidate the contribution of these proteins in the tolerance mechanism to salt and drought. Testing candidate genes in TILLING available wheat population will allow the identification of new alleles conferring abiotic stress tolerance.