Provitamin A maize inbred lines exhibit resistance to multiple foliar diseases under laboratory and field conditions

Maize (Zea mays) is a staple food for millions in sub-Saharan Africa (SSA), contributing to both caloric intake and essential micronutrients. Recent breeding efforts have focused on enhancing its nutritional value by increasing provitamin A (PVA) carotenoid content to address vitamin A deficiency (VAD), a common problem among children under 5 years, pregnant and lactating mothers across SSA. However, high rainfall, and both warm and humid conditions in various SSA regions result in devastating foliar diseases such as maize streak virus (MSV), northern corn leaf blight (NCLB), southern corn leaf blight (SCLB), southern corn rust, grey leaf spot (GLS), and Curvularia leaf spot (CLS). Breeding for resistance can aid in mitigating yield losses caused by those diseases. Rapid, efficient screening methods can allow for examining large germplasm collections. The current study evaluated 21 maize inbred lines with contrasting PVA content, along with two commercial inbred controls, for resistance to Exserohilum turcicum, Bipolaris maydis, and Curvularia lunata, causal agents of NCLB, SCLB, and CLS, respectively, using a detached leaf assay (DLA) and under natural field infestation. Significant variation was detected among the inbreds, seven were classified as resistant to certain diseases, ten as moderately resistant, and six as susceptible to all foliar diseases. Overall, high PVA inbred lines had less susceptibility to NCLB, SCLB, and CLS. The results suggest that PVA-enriched maize inbred lines possess improved resistance to multiple foliar diseases. The field assessments of disease severity validated the effectiveness of the DLA in distinguishing resistant from susceptible inbred lines, and resistance to other diseases in field conditions was detected in parallel. The results indicate that high PVA maize has the potential to simultaneously address VAD, mycotoxin contamination in SSA with improved resistance to multiple foliar diseases.