The provided text traces the evolution of plant breeding from conventional selection-based approaches to modern gene-editing technologies. It highlights how Mendel’s gene concept transformed the theoretical and practical foundations of crop improvement, while emphasizing that the core activities of plant breeders—creating genetic variation, selecting desirable variants, and evaluating promising lines—remain fundamentally unchanged. Molecular tools have, however, made these activities more systematic, precise, and predictable.

The text explains that genetic variation originates from mutations, which may involve changes in DNA sequences or larger chromosomal alterations. Although conventional mutagenesis using radiation and chemical agents has contributed significantly to crop improvement, these methods generally produce random mutations and may cause unintended changes across the genome. This limitation encouraged the development of technologies capable of inducing targeted genetic modifications with greater precision.

The discussion then introduces site-directed nucleases (SDNs), including meganucleases, zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and CRISPR/Cas9. These technologies enable targeted gene inactivation, sequence replacement, allele restoration, and transgene integration. Their development has further supported the emergence of base editing, prime editing, and programmable epigenome editing, expanding the possibilities of modern genome engineering.

The text also emphasizes the rapid growth of gene-editing research and its increasing application in crop improvement. It notes that although numerous gene-edited plant lines have been developed, only a limited number have reached commercialization, with high-oleic-acid soybean and high-GABA tomato cited as examples. It also refers to gene-edited rice varieties identified for release in India, subject to the resolution of intellectual property rights issues.

Overall, the chapter aims to present the major developments in gene editing relevant to plant breeding in a logical and accessible manner. The use of illustrations and tables is intended to simplify complex concepts, summarize procedures, and help readers understand the subject without being overwhelmed by unnecessary technical detail.

Dr. B. D. Singh is a former Professor Emeritus at the School of Biotechnology, Banaras Hindu University (BHU), Varanasi, India. His academic association with BHU reflects his contribution to the field of biotechnology and related areas of scientific education and research.

Dr. Ashok K. Singh is a former Director of the Indian Agricultural Research Institute (IARI), New Delhi, and an Emeritus Scientist in the Division of Genetics, IARI. His professional career reflects extensive experience in agricultural research, genetics, and institutional scientific leadership.

Chapter 1. Introduction to Gene Editing

Chapter 2. Gene Editing Tools. I. Meganucleases, and Zinc Finger and TALE Nucleases

Chapter 3. Gene Editing Tools II. CRISPR/Cas9 System

Chapter 4. Tools for Gene Editing. III. Base Editors and Chimaeric Oligonucleotides

Chapter 5. Gene Editing Tools. IV. Programmable Chimaeric Effectors and Gene Drives

Chapter 6. Gene Editing Procedure for Plants

Chapter 7. Enhanced Crop Yields

Chapter 8. Gene Editing for Quality Traits

Chapter 9. Gene Editing for Stress Resistance

Chapter 10. Gene Editing for Novel Traits

Chapter 11. Gene Editing as a Functional Genomics Tool

Chapter 12. Biosafety, Ethical and Intellectual Property Rights Issues