Clustered regularly interspaced short palindromic repeats- (CRISPR)–Cas9 system for engineering resistance to plant viruses

The Indian economy is based largely on agriculture, which accounts for 18% of total gross domestic product and accounts for approximately 70% of the export earnings of the country. Important crops in India are rice, wheat, pulses, sugarcane, and spices. The India government has targeted doubling farm exports to $60 billion by 2022; however, several plant pathogens, including viruses, are a major limiting factor in achieving this target. Virus diseases are managed by preventive and modern methods. Preventive measures may comprise the control of viral vectors, development of virus-free plants using various methods, and quarantine regulation. However, these controls are not looking promising owing to the development of resistance to pesticides in several virus vectors. The modern methods include pathogen-derived resistance, RNA interference–mediated resistance, and ribozyme-mediated resistance. For the past few years, targeted silencing of viral pathogens has been achieved in plants using clustered, regularly interspaced, short palindromic repeats (CRISPR)–Cas 9 tools. With this technology, targets of multiple viruses at various sites simultaneously has become achievable, and results are quite promising. In this chapter, we discuss the achievements of plant virologists in the development of virus-resistant crops using various popular techniques.