Abstract
The experiment was carried out at the field of College of Agriculture at the University of Duhok during the spring season of 2010. Eleven inbred lines of maize, had been selected, eight of them were used as a line (males), (ZP 204, ZP 301, ZP 595, ZP 670, ZP 430, ZP 505, un 44652, ZP 735) and the reminder used as testers (females), (ZP 197, ZP 607 and ZP 707) to estimate gene action, specific and general combining ability, heterosis and heritability for yield and its components under two nitrogen fertilizer levels (135 and 275 Kg N/ha). The results showed significant positive heterosis for most studied characters of hybrids under two nitrogen levels. The better hybrids for grain yield were (ZP 607 × ZP 505) and (ZP 707 × ZP 204). The line ZP 505 showed the heights positive GCA effect of grain yield. Heritability in broad sense was high for all studied characters while heritability in narrow sense was high for ear height under both nitrogen levels and number of rows / ear under value nitrogen level only. The additive variance was more than dominance variance for all characters except 100 grain weight (g) and ear length (cm) under (135 Kg N). The average degree of dominance was greater than one for all characters. The results of this study can enhance the use of promising inbred lines in a programme focused on developing hybrid that efficiently can take up and use nitrogen.
