Systematic synthesis of CRISPR/Cas applications for enhancing salt tolerance in crops: a decade of progress and challenges

Soil salinity is a major constraint on global crop productivity, driving the need for salt-tolerant varieties. While CRISPR-Cas genome editing offers targeted solutions for trait improvement, significant biological and technical bottlenecks limit its application in conferring salt stress resilience. This systematic summarizes findings from 83 peer-reviewed studies (2015-2024) employing CRISPR/Cas technologies to improve salt tolerance in five major crops (rice, wheat, maize, sorghum, barley). Our systematic review reveals that early single-gene edits achieved modest gains (30-50% Na⁺ exclusion) but often showed limited yield gains in field settings, potentially due to compensatory regulation and environmental variation. The literature suggests that multiplex designs spanning ion homeostasis, osmoprotection, and ROS management can improve salt-tolerance outcomes and help maintain yield under severe salinity; however, the magnitude of benefit varies with crop, genotype, and transformation/regeneration context. Protein-protein interaction networks identified 12 hub genes and three functional modules, highlighting SOS3 and MPK6 as critical bottlenecks whose disruption risks pleiotropic effects. Spatial expression analysis underscored tissue-specific trade-offs, constitutive editing of root-dominant genes in shoots reduced yields by 15-28%, while tissue-optimized promoters minimized physiological conflicts. Persistent challenges include genotype-dependent transformation inefficiencies, epigenetic drift and environmental interactions under salt stress. Collectively, our synthesis consolidates and refines current best practices for salt-tolerance genome editing and highlights major bottlenecks-particularly regeneration/transformability, genotype dependence, and epigenetic constraints-that should be explicitly considered in experimental design and reporting.