Chapter 6 - CRISPR/Cas system for the development of disease resistance in horticulture crops

Abstract

Genetic modification is the key to improve yield, quality, and disease resistance in crops. Since 2013, genome engineering using site-specific nucleases, notably clustered regularly interspaced short palindromic repeats/CRISPR-associated endonuclease (CRISPR/Cas9), has contributed enormously to crop improvement. CRISPR technology has been successfully utilized to improve crop yield, change plant architecture/floral characters, enhance fruit quality, and reduce disease susceptibility. In this chapter, the successful demonstration of engineering disease resistance in model plants, Arabidopsis, tobacco, and horticultural crops like potato, citrus, tomato, cucumber, apple, and grapevine is discussed. Plants exhibit a natural resistance to bacteria, fungi, and viruses through loss-of-function mutations in disease susceptibility loci. The majority of these susceptibility loci are transcription factors that serve as a binding domain for pathogen effectors. Mutational alleles of host transcription factors conferring broad-spectrum disease resistance are restricted to a few crop species. CRISPR/Cas9 toolkit instead is efficient enough to create targeted mutations in the host susceptibility loci of numerous monocot and dicot plants. Besides, the rapid generation of transgene-free mutants and simultaneous editing of multiple alleles in polyploid genomes is possible through CRISPR/Cas9-mediated genome editing. With the future of crop improvement centered on genome editing, this chapter aims to draw the attention toward the accomplishments and the problems of employing the CRISPR/Cas9 system for targeted mutations in host disease susceptibility factors.