Climate-Resilient Soybean: Integrated Breeding Strategies for Mitigating Drought and Heat Stress

Soybean (Glycine max (L.) Merr.) plays a pivotal role in global food security as a primary source of vegetable protein and oil. However, its production is increasingly jeopardized by the frequent concurrence of drought and heat stress, a scenario predicted to intensify under ongoing climate change. While the effects of individual stresses have been well documented, the combined occurrence of drought and heat imposes unique physiological challenges, such as the conflict between stomatal closure for water conservation and transpirational cooling, that critically impair yield stability. This review provides a comprehensive synthesis of the physiological and molecular mechanisms governing soybean responses to these combined stresses, with a specific focus on modifications of root system architecture and the sensitivity of biological nitrogen fixation. We critically analyze recent advances in genomic resources, highlighting key quantitative trait loci (QTLs) and candidate genes identified through genome-wide association studies (GWAS) and multi-omics integration. Furthermore, we propose integrated breeding strategies that bridge conventional breeding with cutting-edge technologies, including high-throughput phenotyping, speed breeding, and CRISPR/Cas9-mediated genome editing, underpinned by high-throughput phenotyping and speed breeding. By presenting a roadmap for developing climate-smart soybean cultivars, this review aims to support sustainable agricultural practices that ensure both adaptation and mitigation in a changing climate.