Introgression of halophytic salt stress-responsive genes for developing stress tolerance in crop plants.

The world's population is increasing daily, with corresponding demands for sustainable food production, but about 800 million ha of land is affected by salt. Salinization is gradually increasing for several reasons, including scanty rainfall, poor irrigation practices, salt ingression and natural calamities. Salinity is considered a major abiotic stress that adversely affects the growth and productivity of crop plants. Commonly, crop plants are salt sensitive (glycophytes) and so cannot grow in the salt-affected areas. Some plants have natural ability to grow in the high saline areas and are known as halophytes. Halophytes require salt to complete their life cycle and are thus considered potential sources for salt-responsive genes and promoters. The salt-tolerance mechanism is a very complex process which is coordinated from stress perception to signal transduction, and thus provides stress endurance. Several potential salinity-stress responsive and tolerance genes have been isolated from halophytes, functionally characterized and explored for developing transgenic crop plants for sustainable agriculture in the salt-affected areas. About one-quarter of the entire Arabidopsis genome responds to salt stress, and so the search continues for promising stress-responsive genes that can modulate physiological traits and metabolic pathways without imposing yield penalties. This chapter focuses on the examination of halophytes for salt-responsive genes, their functional validation and further utilization to engineer crop plants.