Genetic Assessment of Yield Traits and Heterosis in Maize Testcrosses Under Different Soil Nitrogen Conditions

Abstract

Yield trials demand significant time and resources, necessitating efficient data collection on parental lines to optimise breeding programs and reduce costs. This study assessed the correlation between parental traits and hybrid performance, consistency, and predictability of trait expression in F1 hybrids and the heterotic advantage of agronomic traits. A total of 82 parental lines (79 lines and 3 testers) and 237 testcrosses were evaluated alongside 3 standard checks under low- and optimum-soil nitrogen (N) conditions at the Institute for Agricultural Research experimental fields in Zaria and Mokwa during the 2019/20 and 2020/21 growing seasons. Significant genetic variability was observed among parental lines and testcrosses, offering strategic breeding opportunities. Grain yield reductions under low-N conditions (35–95% in inbreds and 1.3–89% in hybrids) highlighted the impact of N stress and the need for N tolerance in maize genotypes. Correlation analysis and repeatability results linked yield improvement in low-N tolerant maize hybrids to the selection of parental lines with superior performance in traits, such as grain yield, stay-green characteristics, and flowering traits. Parental lines P69 and P14, which showed high tolerance to low N and consistent high yields, were identified as valuable genetic resources. Among the hybrids, P65×T2, P66×T3, and P66×T2 stood out, with grain yields exceeding 6000 kg/ha, representing a 42% yield advantage over the best check. These hybrids also demonstrated a high heterotic advantage over their parents and standard checks, indicating their potential for adoption as commercial hybrids in Nigeria.