ABSTRACT:

Developing extra-early, nutrient-dense, and disease-resistant maize is crucial for advancing global food and nutrition security, particularly across sub-Saharan Africa (SSA) and other drought-prone regions where erratic rainfall and foliar diseases like Southern Leaf Blight (SLB) significantly constrain yields. This study presents the first comprehensive evaluation of SLB tolerance, agronomic performance, and nutritional quality in extra-early SAMMAZ provitamin A quality protein maize inbred lines. Twenty biofortified inbred lines, including two checks, were tested under natural SLB infestation across two rainfed seasons. Analysis of variance revealed significant genotypic differences for most traits. Flowering occurred within 59–64 days (anthesis) and 61–66 days (silking), with a mean anthesis–silking interval (ASI) of 2.1 days. High-yielding genotypes, particularly SAMMAZ 58, 63, and 62, displayed short ASI (≤ 2 days), favourable plant height (158–170 cm), optimal ear placement (76–85 cm), good plant and ear aspects (score = 2), and ≥ 1.0 ear per plant. Grain yield ranged from 4.7–8.8 t ha⁻¹, with SAMMAZ 58, 63, and 62 as top performers. Nutritionally, β-carotene (4.7–9.0 µg g⁻¹) and tryptophan (0.070–0.090%) exceeded biofortification targets in several genotypes, notably SAMMAZ 58 and 63. SLB severity scores (1.6–3.5) and AUDPC values (110.7–178.9) identified SAMMAZ 59, 62, 55, and 34 as tolerant. High broad-sense heritability for plant height (91.2%), grain yield (82.4%), β-carotene (84.6%), and tryptophan (79.3%), together with high genetic advance and moderate-to-high GCV, indicated additive gene action and strong potential for selection gains. These results highlight SAMMAZ 58, 63, 62, and 57 as promising donor lines combining earliness, high yield, superior nutritional quality, and SLB tolerance, thus offering valuable genetic resources for breeding climate-smart, nutrition-sensitive maize varieties to strengthen food security in SSA and similar stress-prone regions.