Transgenic and Genome-Edited Maize: Status and Prospect

Maize is a versatile crop with wider adaptability and is grown in most countries (over 170) in the world. Among the food cereal crops, maize has the highest genetic yield potential. In the past two decades, effective utilization of transgenic technology has resulted in the creation of transgenic or genetically modified (GM) maize with enhanced productivity, and resilience to abiotic and biotic stresses, etc. To date, 244 transgenic events in maize have been made commercially available. According to estimates, the adoption of transgenic technology has increased maize yield, reduced CO2 emission, and reduced usage of chemical pesticides and insecticides, which in turn has benefited farmers economically. Although transgenic technology has brought about a new era in maize improvement, concerns about possible hazards to human health and the environment have hindered its widespread adoption. These concerns and low consumer acceptance have prompted the development of alternative technologies for genetic modification such as genome editing. Many genome-edited (GEd) lines developed using genome-editing technology do not have any foreign/transgenic elements. Consequently, such transgene-free plants are genetically similar to, or maybe even indistinguishable from, conventionally bred plants. Hence, such types of GEd crops are not regulated and therefore not considered GM organisms in many countries. Easy and fast commercialization of such GEd varieties is now possible. For instance, low phytate maize and waxy corn are GEd maize which is exempted from stringent regulatory processes and is near commercialization in the United States. It is expected that GEd maize will achieve more public acceptance compared to transgenic maize. This chapter gives an overview of the present and future applications of genetic engineering-based approaches for sustainable crop improvement in maize.