Investigations were made with six Oriental varieties of the tobacco sub-types Prilep, Djebel and Yaka (P-23, P-84, P10-3/2, P-76, Xanthi Djebel-1 and YV 125/3) and fifteen F1 hybrids for the characteristics flowering time and length of the growing period of tobacco in the field from transplanting to the end of harvest. The field trial was set up in 2010 and 2011 at the Tobacco Institute – Prilep in a randomised block design with four replications. All appropriate cultural practices were applied during the growing season. Statistical processing of data was performed by using the analysis of variance (ANOVA).

The aim of this work was to study the mode of inheritance and to detect possible heterotic effects for the above biological characteristics, which will allow a selection of lines with longer growing season, higher productivity and some other positive characteristics inherited from the early-maturing parent. They would be promising genotypes intended for arid regions with poorer soils and a longer growing season.

The period from tobacco transplanting to 50% flowering in parental varieties ranged from 45 to 95 days in Xanthi Djebel-1 and P-76, respectively, while the period from transplanting to the end of leaf harvesting in these two genotypes ranged from 70 to 145 days. There were differences in inheritance of the two stages among hybrids. The most common types of inheritance were partial dominance and dominance. The early-maturing parent dominated in the first period, while the late-maturing parent dominated in the second period and there was also some evidence of heterosis.