Maize is one of the major crops in Indonesia; however, its national production remains fluctuating. The development of high-yielding hybrid maize cultivars with tolerance to low nitrogen is a vital aim to boost the production. The following research aimed to study the heterotic effects in 10 maize F1 half-diallel hybrids, evaluated under two nitrogen levels, to identify the high-yielding hybrids. The experiment layout had a split-plot design with two factors. The main plots received the nitrogen (N) levels (N1: 50% and N2: 100%), while the 10 F1 hybrids, five parental genotypes, and two check genotypes (NASA-29 and Pertiwi-3) entailed placement in the subplots. Calculating the analysis of variance and heterotic effects occurred for growth, ear, kernel, yield, and flowering traits, followed by heatmap and principal component analyses (PCA). The analysis of variance revealed significant interactions of nitrogen levels and maize genotypes for several traits. Heterotic effects were evident across nitrogen levels for all traits. Heatmap and PCA assisted in identifying the heterosis patterns. Overall, the maize hybrid H₉ (P3 × P5) excelled all other hybrids for most assessed traits, indicating better adaptability to low-nitrogen environments for use in the next breeding program.

Keywords: Growth and yield traits, half-diallel hybrids, heatmap analyses, heterosis, maize, nitrogen stress tolerance, principal component analysis

Key findings: The F1 hybrids revealed heterotic effects for studied traits in maize (Z. mays L.) (up to 21% in growth, 48% in ear, 66% in kernel, and -28% in flowering traits). Nitrogen-by-genotype interactions were considerable across all traits, indicating better adoption to low nitrogen stress. The F1 hybrid H₉ (P3 × P5) was superior for almost all traits for further breeding programs’ use. The heatmap analysis and PCA were notably useful in identifying heterosis patterns and potential hybrids.