Application and advantages of CRISPR-based genome engineering approaches in legumes

Recent genome editing techniques using TALEN (transcription activator-like effector nuclease), ZFN (zinc finger nuclease), and CRISPR/Cas9 (clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9 nuclease) systems offer convenient gene editing tools in different legume species. These techniques can be extended for increased legume production, which is naturally constrained due to extreme environmental conditions and changing climatic scenarios. The three genomic editing tools (TALEN, ZFN, and CRISPR/Cas9) have been successfully attempted in legume species including Alfalfa, Lotus japonicus, soybean, cowpea, chickpea, and peanut for several traits like nodulation, disease resistance, oleic acid content, and symbiotic nitrogen fixation. However, legume genome editing is bottlenecked by the non-existence of routine methods of gene editing due to non-robust, non-reproducible, non-reliable legume transformation and plantlet regeneration protocols across species. A critical discussion on success stories and hurdles is needed to update knowledge and develop standardized, robust protocols valid for different species of legumes. The review aims to showcase the applications and advantages of CRISPR-based genome engineering approaches in different legumes. Additionally, it is permeated with beneficial aspects of legumes: economic, social, environmental, and soil health. The review critically discusses the challenges and limitations for sustainable legume production and further connects with the revolutions due to advanced gene-editing approaches such as base editing, prime editing, and CRISPR-Cas13. The success stories and the critical analysis of bottlenecks of genome editing approaches in different legumes will not only create a base for solving the existing drawbacks but also present possible ways to bridge the gaps for increased legume production in future agricultural practices.