HETEROSIS, COMBINING ABILITY AND THEIR RELATION TO THE GENETIC DISTANCE BETWEEN MAIZE LINES AND THEIR HALF DIALLEL HYBRIDS FOR GRAIN YIELD PER PLANT AND

Abstract

A half diallel cross comprising six pure lines of maize (ZP-595, DKC 6418, DK-17, ZP-694, Sgporo from panan and UN 4652) was carried out. The pure lines and their hybrids planted in 5 July 2018 at the farm of Faculty of Agriculture and Forestry, Duhok University using randomized complete block design with three replications to study the combining ability, heterosis and nature of gene action for traits, number of days to silking, number days to tasseling, plant height, upper ear height, leaf area, number of rows per ear, number of grains per row, grain yield per plant, 300 grains weight, ear weight with grains and shelling percent. The combining ability analysis of variance results revealed that mean square of genotypes, general combining ability and specific combining ability was highly significant for all traits indicated the presence of additive as well as non-additive gene effects controlling all traits. However, relative magnitude of these variance components indicated that dominance gene effects were more prominent for most traits. The parents ZP-595 and DK-17 were the best general combiner for most traits, and the hybrid (ZP-595 x ZP-694) showed significant average performance, specific combining ability effects and heterosis in the desired directions for biggest number of characters followed by the two hybrids (DKC 6418 x UN 4652) and (DKC 6418 x Sgporo from panan), and these could be utilized for developing high yielding hybrid varieties as well as for exploiting heterosis. The genetic distance had a significant positive correlation with the hybrid mean performance, its specific combining ability effect and heterosis for leaf area, grain yield per plant and the ear weight with grains. Narrow sense heritability was low for number grains per row, grain yield per plant and ear weight with grains, and moderate for other traits.