HETEROSIS AND COMBINING ABILITY FOR YIELD AND YIELD COMPONENTS IN MAIZE ( Zea mays L.)

This study was conducted at the Experimental Farm , of the Agricultural Research, Faculty of Agriculture , Omer Al-Mukhtar University , Libya, during summer of the two growing seasons 2013 and 2014 . A half diallel crosses comprising six inbred lines yielding 15 hybrids were studied for nine traits to estimate heterosis and the nature of gene action associated with it in both parents and their hybrids. The analysis of variance for combining ability revealed that both general combining ability (gca) and specific combining ability (sca) variances were highly significant for most of the studied traits indicating the importance of additive as well as non- additive types of gene action in controlling these traits. However , variances due to sca were higher in magnitudes than gca for all the studied traits except plant height . GCA to SCA ratios were less than one for most of the traits except for plant height indicating a preponderance of non additive genetic effects over additive effects . Parent P5 among the parental lines was identified as the best general combiner for ear weight /plant (g), kernel weight /plant (g), ear weight and grain yield/ha (ton) , P2 was the best general combiner for 100-kernal weight and P3 for oil (%) and P1 was identified as the best general combiner for number of ears . Four crosses (p2 × p 3 , p2 × p4 , p3 × p 4 and p4 × p6) showed significant positive SCA effects for ear yield (ton) /ha and seven crosses (p1 × p 2 , p 1 × p 5 , p2 × p 5 , p3 × p 4 , p3 × p6 and p4 × p5 ) showed significant positive SCA effect for grain yield (ton) /ha. Heterosis was measured as a deviation from the midparents. The heterobeltiosis of the different crosses was ranged from 13.13 %to 88.40% for grain yield/ha (ton) . The crosses involving p2 ×p5 , p2×p3 , p1×p2 and P4 × P6 produced the highest positive heterosis for grain yield /ha(ton). It would be concluded that these parentalal combinations could be desirable to produce high yielding hybrids. Therefore ,this parents would be involved in the breeding programs to further improve these parents and to produce high yielding hybrids.