Enhancing cowpea productivity in the Indian subcontinent: Physiological insights into rhizobial symbiosis and sustainable nitrogen fixation

Cowpea (Vigna unguiculata) is a vital legume crop in India, valued for its drought resilience, nitrogen-fixing ability, and nutritional benefits. However, its productivity is constrained by abiotic stresses (drought, heat, salinity), poor soil fertility, and suboptimal farming practices. This review examines the physiological mechanisms of cowpea-rhizobia symbiosis, emphasizing strain-specific adaptations that enhance nitrogen fixation under stress. High-efficiency rhizobial strains like COC-10 (salinitytolerant), TAL-1000 (low-phosphorus-adapted), and SB-12 (salt-tolerant) have increased yields by 15–40% in Indian agroecologies. Key physiological markers—leghaemoglobin content, xylem ureides, and nodule SDH activity—are identified for strain screening. Field trials in Karnataka, Andhra Pradesh, and Odisha demonstrate the success of integrated practices, including rhizobiacompost synergy and intercropping, which reduce fertilizer dependence by 40–50%. Challenges such as inoculant stability, farmer awareness gaps, and strain-soil mismatches are addressed through innovations like CRISPR-edited rhizobia and microbial consortia. Policy recommendations include subsidies for alginate-encapsulated inoculants and farmer training programs. By optimizing symbiotic efficiency and adopting context-specific strategies, cowpea cultivation can significantly contribute to sustainable agriculture and food security in India.