The Determination of Heterosis and Combining Ability for Qualitative Characteristics in Tobacco Using Half-Diallel Cross

The experiment was carried out during two seasons in 2021–2023, in a nursery at the Faculty of Agriculture, Tishreen University, Lattakia, Syria, by cultivating three tobacco genotypes: Prilep, Basma, and Baladi. A half-diallel cross was made between different genotypes of tobacco. In the following season, an evaluation of the parents and individual crosses was performed, which were then distributed according to the randomized complete block design (RCBD) with three replicates to estimate the heterosis, general combining ability (GCA), and specific combining ability (SCA), and the nature of gene action of sugar, nicotine, protein, and chloride content. Genetic analysis showed the importance of additive and dominant effects on heredity in all studied characteristics. The variance ratio of GCA to SCA was more significant than the one for nicotine and protein content. Still, the ratio appeared to be less than one for other studied traits (sugar and chloride content). The Baladi parent exhibited a high GCA for sugar and chloride content, while the Prilep parent showed a high GCA for protein content. Further, the hybrid Prilep × Baladi exhibited the highest SCA for sugar, protein, and chloride content with the highest values for heterosis for the studied characteristics.