Legume-based selenium bioavailability for crop and human nutrition: A global meta-analysis

Selenium (Se) plays an important role in plant growth and human nutrition, and its narrow safety margin can cause adverse effects in the legume-based food system. A comprehensive insight is required to understand the precise use of Se to legumes for sustainable agriculture production and biofortification. We conducted a meta-analysis of 1644 pair-wise observations published from 2009 to 2024 and analyzed data by machine learning models (RF, XGBoost, and SVM). Effects of Se fertilizer type, concentration, exposure duration, application method, and growth medium on legume growth and physiology were evaluated. Se application at ≤ 2.5 mg kg^-1 improved shoot dry weight, biological yield, chlorophyll content, and antioxidant enzymes (SOD, POD, CAT, and APX), while reducing oxidative stress related indicators such as H₂O₂. In contrast, elevated Se levels (>2.5 mg kg^-1) reduced yield, germination, disrupted antioxidant defenses, and increased oxidative damage. Se accumulation in legume grains exhibited an exposure-medium dependent response, with the highest accumulation observed under hydroponic conditions, followed by soil applications. Machine learning confirmed Se concentration, fertilizer type, and exposure matrix as dominant drivers of Se impact on legumes. Overall, precise Se application rate ≤ 2.5 mg kg^-1 improves legume performance and supports sustainable legume-based agroecosystem management globally.