Impact of low-rainfall and low nitrogen stress on nutritional quality traits and yield of quality protein maize hybrids

Quality Protein Maize (QPM) has elevated lysine and tryptophan levels, yet the stability of these nutritional advantages under abiotic stress remains largely unknown. This study evaluated the effects of low-rainfall and low Nitrogen (N) conditions on grain yield, and protein, tryptophan, iron (Fe) and zinc (Zn) accumulation in QPM hybrids. Forty QPM hybrids and five checks were tested under optimal, low N, and low-rainfall conditions in Ethiopia and Zimbabwe. Grain nutritional traits were quantified using near-infrared spectroscopy, colorimetric tryptophan assay, and atomic absorption spectrophotometry. Grain yield and micronutrient density were decreased under low N and low-rainfall conditions. Low N reduced protein and tryptophan concentrations, whereas low-rainfall conditions increased total protein. Fe and Zn concentrations declined under both stresses. Zn showed better stability under low-rainfall conditions. Grain yield weakly correlated with almost all nutritional traits. Significant positive correlations were observed between protein and Fe, protein and Zn, and tryptophan and Zn under low-rainfall, and Fe and Zn under low N conditions, indicating the possibility of simultaneous nutrient improvement. Performance under optimal and low N and low-rainfall conditions was associated for yield, protein, tryptophan, and Zn, indicating the possibility of simultaneous improvement of yield and nutritional quality. Selection under optimal conditions may accelerate breeding for stress-prone environments without compromising nutritional value.