Diallel analysis of maize lines with contrasting responses to applied nitrogen

Abstract

Six S₅ lines of maize, previously identified as having contrasting responses to nitrogen (N) supply, were used to carry out a complete series of diallel crosses. The resulting 15 hybrids were grown in a field at two N levels. The general combining ability (GCA) and specific combining ability (SCA) were estimated using the method 4, model I analysis of Griffing for grain yield kernel weight, grain number, harvest index, green leaf number, ear leaf area, N utilization efficiency, total plant N, grain N content, anthesis-silking interval, chlorophyll content and prolificacy. For the majority of the traits, GCA was more important than SCA and there was an increase of non-additive effects under low N. Significant interactions were observed between GCA and N levels for grain yield, grain number and chlorophyll content, indicating the selection of different lines for each N level. The lines with the largest effects of N supply per se on grain yield, were those with the largest effects of GCA for this trait. This association indicates that the response of the lines to N supply, should be considered in breeding programmes in order to achieve acceptable hybrids for environments with both high and low N.