Molecular Plant Breeding 2024, Vol.15, No.5, 282-294 http://genbreedpublisher.com/index.php/mpb 284 Additionally, the genetic base of modern maize varieties has become narrower due to intensive selection, which can reduce genetic diversity and increase vulnerability to new threats. Addressing these challenges requires integrating traditional breeding with modern biotechnological tools to enhance the efficiency and effectiveness of maize improvement programs (Andorf et al., 2019; Lorenzo et al., 2022; Sethi et al., 2023). 3 Introduction to Genetic Engineering in Agriculture 3.1 Definition and principles of genetic engineering Genetic engineering refers to the direct manipulation of an organism’s DNA using biotechnology. This process involves the modification of genetic material to achieve desired traits, such as increased yield, pest resistance, or improved nutritional content. The principles of genetic engineering include the identification of target genes, the use of molecular tools to modify these genes, and the integration of the modified genes into the host organism’s genome (Wu and Li, 2024). Techniques such as CRISPR/Cas9 have revolutionized genetic engineering by allowing precise edits to be made to the DNA sequence, thereby enhancing the efficiency and accuracy of genetic modifications (Lorenzo et al., 2022; Ye et al., 2022). 3.2 Key breakthroughs in genetic engineering relevant to crop breeding Several key breakthroughs have significantly advanced the field of genetic engineering in crop breeding. The development of CRISPR/Cas9 technology has been a game-changer, enabling precise genome editing to improve complex traits such as yield and drought tolerance in crops like maize (Lorenzo et al., 2022). Another notable achievement is the creation of transgenic crops that are resistant to pests and diseases, which has been successfully applied to important crops like rice, wheat, and maize. Additionally, the biofortification of crops, such as the development of Golden Rice enriched with vitamin A, represents a significant advancement in addressing global malnutrition. These breakthroughs demonstrate the potential of genetic engineering to complement traditional breeding methods and accelerate the development of superior crop varieties (Lambing and Heckmann, 2018; Andorf et al., 2019). 3.3 Comparison between traditional breeding and genetic engineering approaches Traditional breeding and genetic engineering are both essential methods for crop improvement, but they differ in several key aspects. Traditional breeding relies on the natural genetic variation that arises during meiosis and involves the selection and crossing of plants with desirable traits over multiple generations. This process can be time-consuming and less precise, as it often involves the transfer of large segments of DNA, including both beneficial and non-beneficial genes (Lambing and Heckmann, 2018; Li, 2020). In contrast, genetic engineering allows for the direct modification of specific genes, providing a higher level of precision and control over the traits being introduced. Genetic engineering can introduce new traits that are difficult or impossible to achieve through traditional breeding, such as resistance to specific pests or enhanced nutritional content. However, uncertainties associated with the insertion and expression of transgenes can pose challenges, and the acceptance of genetically engineered crops varies among different regions and stakeholders. 4 Key Genetic Engineering Techniques in Maize Breeding 4.1 CRISPR-Cas9 and other gene-editing technologies CRISPR-Cas9 has revolutionized the field of genetic engineering, providing a precise and efficient method for genome editing in maize. This technology utilizes the Cas9 endonuclease guided by RNA to introduce targeted double-strand breaks in the DNA, which can then be repaired to create specific genetic modifications. The CRISPR-Cas9 system has been successfully used for targeted mutagenesis, gene editing, and site-specific gene insertion in maize, enhancing traits such as disease resistance, yield, and stress tolerance (Svitashev et al., 2015; Chen et al., 2019; Rajput et al., 2021; Lorenzo et al., 2022). Additionally, other gene-editing technologies like TALENs and ZFNs have been employed, although CRISPR-Cas9 remains the most prominent due to its simplicity and versatility (Arora and Narula, 2017; Eş et al., 2019).
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