Genotype selection in soybean using WAASB and MTSI for seed yield, composition, and fatty acid profiles under irrigated and rainfed conditions

Abstract Soybean ( Glycine max ) seed yield and quality are strongly affected by drought, particularly during reproductive stages. We evaluated 22 genotypes under irrigated and rainfed conditions across three Missouri environments (2023–2024) for seed yield, 100 seed weight, protein, oil, and five fatty acids. Mixed models were used to partition genotype, environment, and genotype × environment effects and to obtain best linear unbiased predictions (BLUPs) for each trait. Seed yield showed strong environmental sensitivity, whereas protein, oil, and most fatty acids exhibited moderate to high broad‐sense heritability ( H 2 = 0.65–0.95), indicating good prospects for genetic gain. Performance and stability were jointly assessed using the weighted average of absolute scores from BLUPs (WAASB) and the multi‐trait stability index (MTSI). WAASB biplots highlighted genotypes G9, G13, and G17 as combining below‐average WAASB with favorable mean performance for seed yield and key quality traits. MTSI rankings confirmed these three lines as the most desirable multi‐trait ideotypes. Selection based on WAASB and MTSI increased mean yield from 2603 to 2775 kg ha −1 (+5.17%) and oil from 17.7% to 17.9% (+1.05%), while slightly reducing protein (−0.49%) and oleic acid (−1.60%) and substantially decreasing linolenic acid (−5.00%), improving oil stability. These results demonstrate that BLUP‐based stability metrics integrated with MTSI provide an effective decision‐support framework for identifying drought‐resilient, high‐value soybean cultivars for variable water regimes.