Emerging trends in transgene-free crop development: insights into genome editing and its regulatory overview

Genome editing tools have revolutionized plant biology research offering unparalleled applications for genome manipulation and trait improvement in crops. Adopting such advanced biotechnological tools is inevitable to meet increasing global food demand and address challenges in food production, including (a)biotic stresses and inadequate nutritional value. Despite reliance on conventional genetic manipulation methods, the CRISPR-Cas-mediated genome editing toolbox allows precise modification of DNA/RNA in a target organism's genome. So far, CRISPR-Cas has been widely used to enhance yield, quality, stress tolerance, and nutritional value in various food crops. However, challenges such as reagent delivery in suitable explants, precise editing with minimal off-target effect, and generating transgene-free plants persist as major bottlenecks in most plant species. Components of CRISPR-Cas construct mainly Cas, guide RNA (gRNA), and selectable marker genes are often integrated into the host genome, which raises regulatory concerns. However, adapting advanced gene-editing strategies, including high-efficiency Cas endonucleases, DNA-independent RNP delivery, morphogenetic regulators, and grafting-mediated editing, are paving the way for transgene-free crop improvement while easing biosafety regulations. Further, regulatory frameworks for genome-edited crops vary globally, with several countries accepting them and others debating their legal status. Hence, the disparity in global regulatory guidelines of genome editing curbs commercialization. The current review highlights the emerging CRISPR-mediated tools or methods and their applications in developing transgene-free designer crops to harness the benefits of advanced genome manipulation.