Plant Mutagenesis Tools for Precision Breeding: Conventional CRISPR/Cas9 Tools and Beyond

Abstract

Plant breeding facilitates the selection of plant populations with the desired trait from the genetic pool. A set of expressed or non-expressed genetic combinations are generally evolved due to spontaneous or induced mutations in the genetic pool of particular plant species. Genetic modification is the basis of diversity that allows domestication alongside adaptation in changing environmental conditions, i.e., from wild to cultivated species. Plant phenotype-based selective breeding has been an efficient way used in the past. Also, induction of random mutations by physical or chemical agents and further selection for desired traits from the mutant library has produced several plant varieties. However, conventional mutagenesis combined with selective breeding has some drawbacks. It makes the random mutations; the process is laborious and slower; it comes with the risk of losing beneficial traits during breeding. In recent times, genome-editing (GE) tools comprising molecular genetic scissors are tailored to precisely target the desired location in the plant genome. The most used GE tool is the clustered regularly interspaced short palindromic repeat-associated (CRISPR/Cas) endonuclease system. The CRISPR-based tools are part of a new technology called new plant breeding techniques (NBTs) that accelerate plant breeding. Diverse CRISPR-based tools have been optimized to achieve expected goals in NBTs like higher yield, tolerance to biotic and abiotic stresses, prevention of post-harvest losses, value addition, and novel traits-in-demand by farmers and consumers. This chapter summarizes an overview of the CRISPR/Cas system, CRISPR-based tools for plant breeding, and recent applications of CRISPR technology in agriculture.