A REVIEW OF CRISPR-CAS APPLICATIONS IN ENHANCING ABIOTIC STRESS TOLERANCE IN CROP PLANTS

Abstract

Abiotic stresses such as drought, salinity, heat, cold, oxidative damage and heavy-metal toxicity reduce crop productivity by disturbing water relations, ion homeostasis, membrane stability, photosynthesis and reproductive development. Conventional breeding has led to the development of important stress tolerant cultivars but many adaptive traits are polygenic, environmentally dependent and linked to yield penalties. CRISPR-Cas genome editing provides an alternative route as it can modify specific genes, promoters, alleles or regulatory elements while maintaining the elite varietal backgrounds. Here we review the current applications of CRISPR-Cas systems for improving crop plant tolerance to abiotic stresses and focus on Cas9 knockouts, Cas12a editing, base and prime editing, promoter engineering and DNA-free delivery of ribonucleoproteins. Data from rice, maize, wheat, tomato and other crops indicate that editing of negative regulators, stress-signaling components, ion transporters and developmental genes can enhance salinity tolerance, drought resilience, heavy-metal management and heat or cold adaptation. But stress tolerance is not a single laboratory phenotype. Useful edited cultivars need to combine stress survival with yield stability, quality, low off-target risk, predictable inheritance, and regulatory acceptability. The most promising future strategy is therefore not indiscriminate gene knockout, but integrated trait design combining genomics, phenomics, transcriptomics, precise editing, multi-location validation and pre-breeding pipelines. Careful target selection, transparent biosafety assessment and realistic field evaluation of CRISPR-Cas tools are likely to accelerate climate-resilient crop improvement.