干旱区生态环境知识资源中心

The devastating consequences of desertification and water scarcity can be seen and felt all over the world. About 3.6 billion of the world’s 5.2 billion hectares of dryland used for agriculture have suffered erosion, soil degradation and salination. Desertification can also have a serious impact far beyond the borders of directly affected countries, can hinder efforts for sustainable development and introduces new threats to human health, ecosystems and national economies. Forced migration and potential for inter-state conflict add to the urgency of this global problem. Therefore, solutions are desperately needed, such as the improvement of drought and salinity tolerance of crops. A more recent idea is to take advantage of the genetic potential of crops still have (Glenn et al., 1998). This idea requires to first identify accessions of a crop species showing enhanced drought and/or salt tolerance. Another promising approach under discussion is to use (xero-) halophytes instead of glycophytic crops or to transfer genes from halophytes to regular crops to enhance their salt resistance. Halophytes grow in a wide variety of saline habitats, from coastal regions, salt marshes and mudflats to inland deserts, salt flats and steppes (El Shaer, 2003). Halophytes are introduced already at many sites to valorize highly salinized zones and non-conventional water resources such as waste water. However, the sustainable use of these plants depends under osmotic and ionic stress on the ability to exhibit a wide range of responses at molecular, cellular and whole plant levels. This includes the synthesis of compatibles solutes/ osmolytes, specific proteins and radical scavenging mechanisms, ion uptake and compartmentation of injurious ions. Acclimation of these plants to salinity depends also upon activation of cascades of molecular networks involved to stress sensing, signal transduction and the expression of specific stress-related gene and metabolites. The product of these genes may participate in the generation of regulatory molecules such as plant hormones. The deeper understanding and replicability of the physiological and biochemical basis of drought and salt resistance can provide a basis for the cultivation of suitable plants in regions threatened by desertification and water scarcity sustainable culture conditions. Even the drylands could offer tangible economic and ecological opportunities. The aim of this chapter is to screen the responses of halophytes with regard to drought and salt resistance to identify early indicators allowing successful breeding (Koyro et al., 2009).