Inadequacy of rainfall is one of the negative impacts of climate change globally. Productivity of crops grown in drought or water deficit conditions is greatly reduced which resulted in decline in food production. Conventional breeding has contributed to our knowledge on responses of plants to drought condition. However, limited progress was achieved because response to water-deficit stress by plants is complex and under the control of several genes. Within a short period, researches in Molecular Biology and Biotechnology have greatly increased our understanding of drought resistance in plants. This knowledge is currently being applied to develop water-stress tolerance crop varieties by classical breeding and transgenic approach. This paper documents gene-based techniques and recent discoveries that facilitated development of water stressed-tolerant crops by transgenic approach. Molecular techniques and resources currently being used to increase our knowledge on mechanism of drought tolerant in plants are genomic and complemenary DNA (cDNA) library, polymerase chain reaction (PCR), GenBank database, micro array technology, gene cloning, nucleic acids hybridization and genetic engineering. The conclusion of genome sequencing project on Arabidopsis and rice made possible the discovery of several genes directly or indirectly regulating drought responses in these model plant species. Genes performing similar role in other plants are being discovered in large number using the insights gained from the model species through comparative genomics. Both functional and regulatory genes control biochemical and physiological responses of plants to drought. Through tissue culture and genetic engineering, expression pattern and regulation of drought tolerance genes and their transfer across plant families for development of drought tolerance crop lines were facilitated. Somatic cotyledon, immature embryo, shoot meristem, shoot apex and embryogenic callus are some of the plant tissues being used to incorporate foreign drought resistance gene into cultivated crops. Agrobacterium tumefaciens-mediated method is the most widely used gene transfer technique for developing drought tolerant crops. The paper discussed the need to use biotechnology tools to discover more drought tolerance genes among indigenous plants and incorporate the discovered drought tolerance genes to indigenous cultivated crops for their improvement against water stress. Potential areas of application of the technology and its requirements are also discussed.
Keywords: Capacity building, climate change, conventional breeding, developing countries, drought, gene, genetic engineering, low productivity, potential, promoters, techniques, tolerant, tool, resources, requirement