Field experiment was carried out at field of Agriculture College-University of Baghdad- Abu-Ghraib in spring and fall seasons of 2016. Six inbred lines of maize Sy-33, ART-B17, Sy-52, Inb-27, MGW-16 and Pio-36 entered in half diallel cross to produce 15 hybrids in spring season of 2016. Seeds of parents and hybrids have been planted at the farm in fall season of 2016, using Randomized Complete Block Design (RCBD) with three replicates, to study the genetic behavior of parents and hybrids to improve the same traits, by using the best hybrid vigor, combining ability and estimate some genetic parameters, according to Griffing method 2, model 1, in growth and yield components traits. Results of analysis of variance showed that mean square of genotypes was significant in most of studied traits. The inbred line Sy-52 was the best in most traits and gave the highest mean in grain yield per plant 173 g. The hybrid Inb-27×MGW-16 was gave highest mean for number of grains per row 41.8 and for grain yield per plant 163 g. The hybrid MGW-16×Pio-22 was the superior than the hybrids others for heterosis measured as a deviation of F1 from best parents and gave highest hybrid vigor for grain yield per plant 47.82%.
Results genetic of analysis showed that mean square due to GCA and SCA were highly significant differences in most traits. The variance ratio of σ2sca σ2gca appeared less one for all traits, indicating to be that dominance effects controlled these traits. The parental line Sy-52 had the significant GCA effect for number of rows per ear 0.67 and for grain yield per plant 13.15, the hybrid Inb-27×MGW-16 showed the highest significant SCA effect for grain yield per plant 27.98. The values of dominance genetic variance were more than values of additive genetic variance for all studied traits. The broad sense heritability was high for all studied traits, while the narrow sense heritability was low in most traits. The average degree of dominance was more than one for all studied traits. The genetic advance percentage ranged between low and medium for all traits.