The investigation was carried out during 2013–2014 in the experimental field of the Dobrudzha Agricultural Institute – General Toshevo (DAI). Four hybrid combinations of oil seed sunflower were studied, which were obtained from the crossing of four sterile lines with four fertility restorers. The correlation coefficient, the actual leaf area of the entire plant and the leaf area compared with the mean value for the lines and the hybrid combinations were determined. Two-factor dispersion and variation analyses were applied for statistical processing of the results using the XLSTATPro. ver 7.0.1 software.
The obtained results demonstrated the difference between the leaf area calculated by applying two methods of investigation on the parental components and the hybrid combinations, involving a correlation coefficient for the purpose. The relationship between the size of the leaf area and the yield was studied.