Resistance to Abiotic Stress: Theory and Applications in Maize Breeding

Maize, being a widely adapted crop, cultivated across the globe, is supporting both livelihood security and food security of mankind. Cultivated maize is more prone to abiotic stresses as compared to their wild counterpart. Natural mutation followed by natural and artificial selections contributed to yield gains in maize. However, due to the hindrance posed by the abiotic stresses, genetic potential of maize could not be realized to the fullest. Many plant breeding interventions were made to utilize the available genetic resources to breed for stress resilient maize. However, efforts made to breed for high yielding maize through traditional plant breeding approaches and improvement achieved are not matching with the demands. To understand the target traits, geneticist and breeders dissected the traits using modern tools and techniques. Genetic mapping of yield and yield component traits under abiotic stresses opened the new way of marker assisted maize breeding for stress tolerance. Development of different trait specific breeding populations supports the novel findings. Fine mapping and positional cloning experiments provided clear understanding of complex traits like abiotic stresses. The approaches like forward breeding using molecular markers and genomic selection are increasingly becoming cost effective new tools for breeders to accelerate the process of new cultivar development with increased tolerance to abiotic stresses. Genetic variations not present in the wild or cultivated species of maize are also utilized in genetic improvement of maize by transgenic approaches. This has resulted in effective utilization of cross boundary information across different and /or unrelated species. Though the technique is robust, considering societal taboos, this approach has been given less encouragement. Alternate to this, genome editing approach played a remarkable role in improving target traits in maize. The modification in ARGOS gene is one of the landmark achievements in drought tolerance in maize. The specificity of genetic alteration followed by gain in genetic improvement will further be enhanced by base editing techniques. Maize being a well-studied model plant and various breeding concepts have been derived by understanding the genetics of traits; application of novel breeding approaches will certainly favor breeding for stress tolerance.