Engineering crops for tolerance against abiotic stress through gene manipulation

Plant genetic engineering took birth in the mid-eighties when, for the first time, plants were successfully engineered for improved virus, herbicide and insect resistance. This sphere has been ever-increasing since then. Abiotic stresses (such as high salt levels, low water availability leading to drought, excess water leading to flooding, high and low temperature regimes, etc.) adversely affect crop plants. The genetic responses of plants to these stresses are complex involving simultaneous expression of a number of genes. Till the early-nineties it was inconceivable that there would be any success in attaining the goal of improving resistance of crop plants to abiotic stresses. Continuing efforts of the stress biologists have resulted in engineering of plants resistant to low temperature, high temperature and excess salinity. A satisfactory progress has also been achieved in the area of generating plants resistant to water stress and flooding. While what has been achieved is impressive, it is still a challenging task to pyramid useful genes for high-level resistance to such stresses. The limiting factor in extension of biotechnology to abiotic stresses is the lack of information on what are the 'useful genes'-genes which would lead to better stress tolerance. We have reviewed how these genes are being searched to enable further development of strategies for stress management in crop plants. This is important because the strategics for coping with the abiotic stresses (and also for several other applications in plant biotechnology) have also come through the research work of scientists working on as diverse organisms as bacteria and fish