Agronomic variation and trait associations among maize genotypes under Terai conditions of Nepal

Maize (Zea mays L.) is an important cereal crop in Nepal, and evaluating agronomic variation among genotypes is essential for identifying promising materials for further testing. This study assessed agronomic variation and trait associations among 24 maize genotypes under farmer-managed field conditions in Sundarharaicha, Morang, Nepal. The experiment was conducted using a randomized complete block design with three replications. Significant genotypic variation was observed for several vegetative, reproductive, and yield-related traits. RML152/RML96 recorded the greatest plant height and ear height, whereas RH10 exhibited the lowest values for both traits. RL35-1/RML2001 produced the highest number of grains per row, while RML142/RML17 recorded the highest test weight and grain yield (6482.65 kg ha−1), followed by SULTAN (6322.17 kg ha−1) and RL35-1/RML2001 (6160.90 kg ha−1). RH10 recorded the lowest grain yield (3312.83 kg ha−1). Principal component analysis showed that the first four components explained 82.0% of the total variation, with the first two accounting for 56.1%. Correlation analysis based on genotype means revealed strong positive associations between plant height and ear height (r = 0.92) and between days to anthesis and days to silking (r = 0.99). Grain yield was strongly and positively associated with test weight (r = 0.86) and was also positively associated with cob length and number of grains per row, whereas the anthesis–silking interval showed a significant negative association with grain yield. Genetic parameter estimates indicated differences in variability and heritability among traits. Overall, RML142/RML17, SULTAN, RL35-1/RML2001, and RML5/RML17 emerged as promising genotypes based on grain yield and selected yield-related traits. Further evaluation across multiple locations and seasons is required to assess their yield stability and broader adaptation under Nepalese production conditions.