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.