Diallel Analysis of Maize for Leaf Angle, Leaf Area, Yield, and Yield Components1

Abstract

The 15 possible single‐crosses among six maize inbred lines (Zea mays L.) were grown at three population densities and two leaf conditions (all leaves removed below the ear vs. no defoliation). Three of the six parental lines had relatively small leaf angles while the other three had relatively large leaf angles.The interreationships among leaf angle, grain yield, leaf area, ear size, and prolificacy were examined, and a diallel analysis of combining ability was calculated based on the fixed model. Therefore, the findings reported apply only to the six parental inbred lines included in this study.Defoliation resulted in yield reductions, ranging from 22 to 73%, and leaf area index (LAI) values were reduced by 53 to 68% among hybrids. Upright‐leaf by upright‐leaf (small leaf‐angle) hybrids averaged 42% reduction in yield associated with leaf removal, while upright‐leaf by horizontal‐leaf (large leaf angle) hybrids experienced an average reduction in yield of 39%.For hybrids in this experiment, leaf angle, from vertical orientation, was negatively correlated with yield and with the yield components: grain weight/ear and number of ears/100 plants. LAI was positively correlated with yield, the two yield components, and population density. Plant density was negatively correlated with the two yield components.General combining ability (GCA) and specific combining ability (SCA) effects appeared to be equally important in the expression of leaf angle. One parental line with the upright‐leaf habit exhibited a high GCA value for small leaf angle. There were significant differences in SCA estimates for small leaf angle among the three upright‐leaf inbreds. GCA effects were relatively more important than SCA effects for grain yield, leaf area, ear size, and prolificacy. Population density affected the magnitude of combining ability estimates for certain variables among some crosses.