Medici, L. O. and Pereira, M. B. and Lea, Peter J. and Azevedo, Ricardo A. (2004) Diallel analysis of maize lines with contrasting responses to applied nitrogen. Journal of Agricultural Science, 142 (5). pp. 535-541. ISSN 0021-8596
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.
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