Multi-Trait Evaluation of Soybean (Glycine max L.) Genotypes for Seed Yield, Oil Productivity, and Water Productivity under Semi-Arid Irrigated Conditions

Abstract

Background: Soybean (Glycine max L.) is a globally important source of vegetable protein and oil, and genotype selection is a key lever for improving productivity and water productivity in irrigated semi-arid production systems. Objective: This study evaluated ten soybean genotypes for seed yield, oil yield, oil content, protein content, water use efficiency (WUE), and oil water productivity under semi-arid irrigated conditions, with irrigation water held constant across genotypes so that observed differences reflect genotypic performance rather than irrigation-treatment effects. Methods: The experiment followed a randomized complete block design (RCBD) with genotype as the treatment factor and replication as the blocking factor (10 genotypes × 3 replications = 30 experimental units). Analysis of variance (ANOVA) was performed for each trait, genotype means were separated using the least significant difference (LSD) test at α = 0.05, and genotype relationships were further examined using Pearson correlation, principal component analysis (PCA), Ward hierarchical clustering, and a weighted multi-trait selection index. Results: Genotype effects were highly significant for seed yield (F = 118.90, P = 3.568 × 10⁻¹⁴, CV = 3.85%), oil yield (F = 31.62, P = 3.116 × 10⁻⁹, CV = 8.69%), and WUE (F = 151.68, P = 4.165 × 10⁻¹⁵, CV = 3.75%). Genotype G10 (an imported drought-tolerant genotype) recorded the highest seed yield (4.96 t ha⁻¹), oil yield (1.033 t ha⁻¹), WUE (0.954 kg m⁻³), and multi-trait selection index score (93.3 of 100), followed by G9 (a local genotype from Abu Ghraib) and G8. Conclusion: Under semi-arid irrigated conditions with constant water supply, genotype identity was the principal driver of productivity and water-productivity differences among the ten soybean genotypes evaluated, and G10, G9, and G8 emerged as the most promising genotypes for seed yield, oil productivity, and water productivity.