Parent–Progeny Relationships between Maize Inbreds and Hybrids: Analysis of Grain Yield and Its Determinants for Contrasting Soil Nitrogen Conditions

Most research in maize (Zea mays L.) parent-progeny relationships has focused on heterosis for plant grain yield (PGY) determination, whereas nonheterotic effects for traits other than PGY has remained less explored. Our objectives were to analyze (i) frequency distribution and phenotypic plasticity for 29 eco-physiological traits in different genotypic groups (6 inbreds and 12 hybrids) and environments, (ii) parent-progeny relationships for these traits as well as variations in these relationships caused by contrasting growing conditions, and (iii) direct and indirect effects of traits measured in inbreds on hybrid PGY determination. Genotypes were cropped in the field at two contrasting N levels during three growing seasons. Range in phenotypic plasticity was (i) similar for inbreds and hybrids, (ii) largest for traits such as PGY and nitrogen use efficiency (NUE), and (iii) smallest for traits such as time to flowering and kernel weight. Inbred phenotype was usually (26 traits) a good predictor of hybrid phenotype, but analysis of standardized data demonstrated that (i) for nine traits (e. g., PGY, kernel numbers) this relationship was exclusively driven by environmental effects, and (ii) for the other traits there was a true genetic control. A high correlation (r > 0.26; P <= 0.024) was established between hybrids PGY and 12 traits measured in inbreds, among which we distinguished NUE and ear growth rate for their high direct effect and participation in the indirect effect of other traits.