2026 Vol-6 Issue-2 | GENETIC EVALUATION OF EARLY-MATURING PROVITAMIN A MAIZE (Zea mays L.) INBRED LINES FOR TOLERANCE TO COMBINED DROUGHT AND HEAT STRESS IN NIGERIA

This study evaluated the combining ability and stress tolerance of 50 early-maturing provitamin A maize inbred lines using a line × tester mating design. The lines were crossed to four elite provitamin A inbred testers to generate single-cross hybrids, which were evaluated under combined drought and heat stress and optimal conditions across multiple locations in Nigeria. Data were collected on key agronomic traits, including days to 50% anthesis and silking, plant height, and grain yield. Analysis of variance revealed significant mean squares for general combining ability (GCA) and specific combining ability (SCA) for grain yield and most other measured traits under both stress and non-stress environments. Thirty-six inbred lines demonstrated promising levels of tolerance to the combined stresses. Among the hybrids, TZEIOR 172 × TZEIOR 108 and TZEIOR 202 × TZEI 25 were the highest yielding and most stable across contrasting environments. The hybrid TZEIOR 202 × TZEIOR 164 performed best specifically under combined drought and heat stress. Inbred lines such as TZEIOR 201 and TZEIOR 202 exhibited significantly positive GCA effects for grain yield across environments, making them valuable donors for breeding programs targeting multiple-stress tolerance and provitamin A enhancement. The findings identify superior inbred lines and hybrids that can serve as immediate candidates for further testing and potential release, while also providing valuable parental materials for the development of climate-resilient varieties in sub-Saharan Africa.