**12. Gene and genome editing**

Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism's DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome. Several approaches to genome editing have been developed. A recent one is known as CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9. The CRISPR-Cas9 system has generated a lot of excitement in the scientific community because it is faster, cheaper, more accurate, and more efficient than other existing genome editing methods. Precise genome editing started when for the first time, it was seen that DNA binding zinc finger domains along with Fok1 endonuclease domains could cleave DNA at defined regions and act as site-specific nucleases (SSNs) [63]. Further research led to the development of transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindrome repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). Meganu- cleases (MegaN) recognize long DNA sequences that are greater than 14 nucleotides (nt) up to 40 nt. Since they have endonuclease activity, they produce double-stranded (ds) breaks at the recognition sites [64]. CRISPR/Cas9 is easy to use and is therefore, more popular compared to other genome editing technologies [65]. CRISPR/Cas9 comprises of two components: a single-guide RNA that is customizable and Cas9 endonuclease. Protospacer adjacent motif (PAM) (5′NGG3′) is a prerequisite needed for inducing ds breaks at the targeted sites in the genome. The breaks are repaired through either homology directed repair (HoDR) or non-homologous end joining (NHEJ). Since NHEJ is error- prone, repair leads to insertions or deletions at the target site. CRISPR/Cas9 has shown promising results for crop improvement, and for several nutritional traits and biotic and abiotic stress resistance [65].

Technologies like molecular breeding and genetic manipulation help to achieve food security and resilience to various biotic and abiotic stresses. Advances in NGS technology have enabled the incorporation of genomics with various disciplines of crop breeding. Large-scale genomic markers and high-throughput genotyping have accelerated improved cultivar development in terms of cost and resources. Functional and comparative genomics have provided the platform for gene discovery and gene functional characterization. The key gene or genes regulating a molecular pathway are being genetically engineered to breed phenotypically

improved crop lines. Conventional approaches together with biotechnological tools aim to increase productivity per plant and minimize yield loss at the farmer's level. The collaborative research investments in both the approaches are indispensable to food security and sustainable crop improvement.
