Vol. 6, Issue 2, Part A (2024)

The present study evaluated the physiological and quality responses of eight Sudanese onion (Allium cepa L.) genotypes Abu Sabein, Wad Hamid, Zeidab Red, Shendi White, Texas Grano, Bombay Red, N-53, and Hybrid Super Star under varying levels of soil salinity and water stress to identify tolerant genotypes for sustainable production in semi-arid environments. A split-plot randomized complete block design was employed with three salinity levels (0, 4, and 8 dS m⁻¹) and three irrigation regimes (100%, 75%, and 50% of ETₐ). Physiological parameters such as relative water content (RWC), membrane stability index (MSI), Na⁺/K⁺ ratio, and proline accumulation were measured alongside yield and bulb-quality traits, including total soluble solids (TSS), dry matter, and pyruvate concentration. The results revealed significant main and interaction effects of salinity, water stress, and genotype on onion performance. Yield reduction under combined high salinity and severe water stress ranged from 20% to 38%, with Hybrid Super Star, Abu Sabein, and Texas Grano exhibiting the highest tolerance indices (0.76-0.80). These genotypes maintained superior RWC, higher MSI, and lower Na⁺/K⁺ ratios, demonstrating efficient osmotic adjustment and membrane integrity. Moderate stress induced an increase in TSS by up to 0.9 °Brix, suggesting a potential improvement in bulb sweetness and storage quality. Correlation and regression analyses identified RWC and MSI as the most reliable physiological predictors of yield stability, whereas the Na⁺/K⁺ ratio showed a strong negative association with stress tolerance. The study concludes that the integration of physiological screening with yield-quality assessment provides a robust framework for developing and recommending stress-resilient onion cultivars. Practical interventions such as selective breeding, improved irrigation scheduling, and salinity management can significantly enhance onion productivity and quality in Sudan’s irrigated farming systems facing increasing salinity and water scarcity.