Trait variation in maize across social, physiological, and genetic scales

Maize (Zea mays L.) is a key staple crop in Nigeria, underpinning household food security, dietary protein intake, and rural livelihoods. Despite its importance, productivity in rainfed systems is increasingly threatened by recurrent drought, while differences in the nutritional quality of commonly grown varieties remain poorly characterized within the context of farmer management and local environments. This thesis addresses these challenges through two interconnected studies. The first study examined grain protein content and farmer varietal preferences in Ilorin South, Kwara State, Nigeria. Grain samples collected from smallholder farms were analyzed to compare three maize types: white, yellow, and red. Protein levels differed across both varietal type and location. Yellow maize generally recorded higher protein concentrations than white maize, whereas red maize showed intermediate values, indicating that both genetic background and growing conditions shape nutritional outcomes. A structured survey complemented the laboratory analysis by documenting farmer experiences with drought, seed sourcing, and cropping decisions. White maize was most widely cultivated, largely due to cultural and market preferences. Yellow maize also showed notable adoption, often associated with improved seed and perceived tolerance to dry conditions. Many farmers cultivated multiple varieties simultaneously as a strategy to reduce climate-related risk, and most relied on farm-saved seeds. The second study evaluated drought response and plant–water relations in maize germplasm developed for genetic analysis. Five F₂ lines were grown under well-watered and water-limited treatments in controlled conditions. Water deficit reduced soil moisture and influenced key physiological traits, with significant variation observed among lines. Measurements of stomatal density, carbon isotope composition (δ¹³C), and intrinsic water-use efficiency suggested that internal physiological regulation, rather than stomatal number alone, was central to drought adaptation. Overall, the findings demonstrate that improving maize systems requires integrated attention to nutritional quality, genetic variation, environmental stress, and farmer decision-making.