COMBINING ABILITY, GENE ACTION AND HETEROSIS IN MAIZE (ZEA MAYS L.)

Five maize pure lines (HS, ZP301, IK58, OH40 and DK17) were used in half diallel cross to develop 10 single crosses. Pure lines and their crosses were planted at Al-Qubba, Telkeef (Nineveh Governorate) in ist July 2013 using randomized complete block design with three replicates. General combining ability effects for lines, specific combining ability effects for hybrids, heterobeltiosis as deviation from better parent, genetic variance components and narrow sense heritability were estimated, and adoption of the graphic analysis method for traits, number of days to 50% tasselling and silking, plant height, number of grains per row, 300 grain weight and grain yield per plant. The results showed that mean square of genotypes, parents, crosses, general and specific combining abilities was highly significant for all trairs. The pure line DK17 characterized by desired highly significant general combining ability effects for all traits except 300 grain weight (not significant), and the two crosses (ZP301 x DK17) and (OH40 x DK17) by significant desirable specific combining ability effects and heterobeltiosis for most traits including grain yield per plant. Additive genetic variance components were not significant from zero for most traits, while dominance components were significant for all traits. The values of dominant components were more than that of additive for all traits. Graphic analysis suggested the absence of epistatic gene action (non-allelic interaction) for all traits. Narrow sense heritability was low for grain yield per plant (8.3445%) and moderate for other traits.