Legumes: Breeding Strategies and Adaptive Traits for Drought Tolerance

Abstract

Legume crops such as chickpea, cowpea, common bean, lima bean, mung bean, faba bean, and lentil are vital to global agriculture due to their nutritional value, environmental benefits, and role in sustainable farming systems. Rich in protein, fiber, and micronutrients, legumes support low-input farming, particularly in arid and semi-arid regions. However, their productivity is increasingly affected by drought and other climate-related stresses. This review synthesizes current knowledge on breeding strategies and adaptive traits that enhance drought tolerance in legumes. Key traits contributing to water-use efficiency and yield stability under stress include early flowering, stay-green phenotype, deep rooting, enhanced root hydraulic conductivity, and strong antioxidant-based defense mechanisms. Physiological indicators such as canopy temperature depression, chlorophyll retention, relative water content, and membrane stability also play crucial roles in legumes for drought adaptation. The review emphasizes the importance of genotypic variability and trait heritability across legume species, which serve as resources for developing climate-resilient varieties. While conventional breeding methods such as pedigree and recurrent selection have driven past progress, modern approaches like marker-assisted selection, genomic selection, GWAS, and CRISPR-based gene editing are now accelerating genetic gain in legume crops. Despite these advancements, challenges remain, including limited multi-environment testing, underutilization of wild germplasm, inadequate phenotyping tools for complex traits and poor adoption of improved cultivars. Addressing these requires a systems-based breeding framework that combines genomics, high-throughput phenotyping, and participatory approaches. Integrating adaptive traits with innovative breeding tools will enable the development of drought-resilient, high-yielding, and nutritionally rich legume cultivars, supporting food security and sustainable agriculture in a changing climate.