**1. Introduction**

Plant genome engineering aims to modify crops by incorporating agronomically desirable traits, which could not be achieved through conventional plant breeding methods. Genetically modified crops vary considerably from genetically engineered crops in that the former recruits the modification through both natural and artificial means, whereas the latter is distinguished only by artificial means that would not

occur naturally. Genetically modified (GM) crops have proven to be great complement to conventional crops in meeting global demands for increased yields, increased food security, decreased pesticide use, and higher nutritional quality. The modified composition of fatty acid, protein and increased micronutrients, resistance to pests and disease, male sterility, quality characters like anti-allergy factors, reduced contents of anti-nutritional factors and toxic substances and medical benefits among which herbicide and pest tolerance are more remarkably exploited. The genetically modified herbicide tolerance crops occupy more than 90% of the total cultivated area of genetically engineered crops as the mode actions of herbicides are familiar and tolerant gene sources are more obtainable in wild weedy forms and microorganisms, which paved way for transformation by altering the structure and functions of rate-limiting enzymes without affecting the normal functionalities of plants. In terms of global acreage, genetically modified soya beans are widely cultivated followed by maize, cotton, canola, and alfalfa. However, apart from genetically modified crops, genome-edited crops are generated by nullifying the negative effects of traits of interest while up-regulating the positive effects of the target traits. Genetically modified crops benefit humanity by increasing the availability and quality of food and medical care, as well as contributing to a cleaner environment and alleviating hunger and disease around the world. In this chapter, a detailed discussion addressing the global need for resistance to insect pests, disease, herbicide tolerance, stress tolerance, quality improvement, male sterility and yield improvement through genetic modification in crop plants have been made.
