Full diallel crosses conducted to test combining ability for diallel crosses of tobacco (Nicotiana tabacum L.) crosses using three cultivars; Corjo (A), Sumer48 (B) and Croillo (C), during 2004, at the field of Field Crops Dept., Coll. of Agric. Univ. of Baghdad. Hybrid trial carried out in the green house using randomized complete block design with 3 parents, 6 crosses and 2 control, Habana and CV. 48.
Significant differences were found among parents and crosses in studied characters except dry leaf thick. The crosses (BXC) and their reciprocal cross (CXB) superior in leaf length, leaf width and leaf area. The crosses (AxB) and (BxC) produced highest dry leaf weight 3.48. t/ ha. Positive and negative heterosis were found in all the studied characters in hybrids.
Genetic parameters analysis revealed , that the average degree of dominance was higher than one and broad since heritability were higher in all the studied traits except leaf area. These results indicate that those characters under non additive gene action. It was recommended the crosses (BXC) and (AXB) because their superiority in dry weight of leaves and study of their speed ignition. We also recommend hybridization method in tobacco improvement.