Male Sterility Systems in Hybrid Rice Development for Abiotic Stress Tolerance: A Systematic Review of Genetic Sources, Molecular Mechanisms, and Breeding Strategies

<ns4:p>Research Background Climate change-induced abiotic stresses, alongside rising global food demand, have increased the urgency to develop hybrid rice cultivars with greater productivity, yield stability, and environmental adaptability. Male sterility-based breeding systems play a pivotal role in hybrid rice improvement, while recent advances in molecular technologies have accelerated the incorporation of stress-tolerant traits. This study, therefore, aims to systematically evaluate hybrid rice breeding strategies based on male-sterility systems for abiotic stress tolerance and to identify emerging trends, technological advances, and remaining research gaps. Methods A systematic literature review (SLR) was conducted on studies published between 2017 and 2026. Using the PRISMA framework and PICO-based eligibility criteria, 33 articles were selected for analysis. Descriptive and thematic synthesis methods were applied to assess developments in male sterility systems, molecular breeding approaches, stress-response mechanisms, and experimental designs used in hybrid rice research. Results The findings show that the three-line system based on cytoplasmic male sterility (CMS) remains the most widely adopted breeding platform because of its reproductive stability, efficient fertility restoration, and extensive commercial use. Advances in molecular breeding—including QTL introgression, marker-assisted backcrossing, genomic selection, and CRISPR/Cas9 genome editing—have strengthened the development of stress-resilient hybrids by targeting ion homeostasis, osmotic regulation, antioxidative defense, and root architecture. Nevertheless, important limitations remain. Most studies examine only single-stress environments, despite the growing occurrence of multiple and sequential abiotic stresses associated with climate change. Moreover, the dominance of controlled-environment experiments restricts the broader applicability of findings under heterogeneous field conditions, where genotype–environment interactions strongly affect hybrid performance. These findings underscore the need for integrated breeding frameworks combining multi-trait pyramiding, multilocation field evaluation, and the integration of multi-omics technologies with physiological characterization to accelerate the development of climate-resilient hybrid rice cultivars.</ns4:p>