COMBINING ABILITY FOR NITROGEN USE IN A SELECTED SET OF INBRED LINES FROM A TROPICAL MAIZE POPULATION

Abstract

Tolerance rather than resistance, is the crop response mechanism sought bymaize breeders for cultivation under low levels of nitrogen. Although improved nitrogen use isin intensive research by maize breeders, little is known about its inheritance on tropical maizegermplasm. The objectives of this study were to evaluate the N use through yield and othertraits, and to determine the importance of general (GCA) and specific (SCA) combining abilityeffects in the inheritance of N use, for yield, using a diallel of crosses among a selected set oftropical maize lines under two levels of N. A comparison of relative magnitudes of GCA andSCA for ear yield (EY) suggests that this trait was governed more by dominance than additivegene action, and the contribution of additive genes for nitrogen utilization efficiency decreasesunder N nutrient shortage. Since, for this set of lines, only non additive effects were significantfor this trait, the lines with favorable SCA could be used as donors of N use efficiency in ahybrid development program. The line L2 was identified as being the most suitable combiningoverall parents in this study for improving EY. The crosses L 3 x L 7, L 1 x L 2 and L 7 x L 10showed to be promising combinations based on the significant SCA effects for lines and hybridsdevelopment. The results of this study can enhance the use of promising inbred lines in a programfocused on developing hybrid that efficiently can take up and uses nitrogen.

Keywords

• Zea mays L.
• nitrogen stress
• general and specific combining ability
• yield