Combining ability of early op varieties of sunflower

The combining ability of 15 early OP varieties was studied. The middle level of combining ability was pointed out for Sibirsky 91, Sibirsky 97, Kulundinsky-1, Bogucharetz, Skorospely, Skorospely 87, Meteor, Chakinsky 931, Voronezsky 638 and R-453 (Rodnik). A good combining ability had Chakinsky 602, VNIIMK 8883 and Buzuluk. A new variety Buzuluk has stable GCA for yield and oil yield per hectare. Enisey and Krepysh had low level of this character. The use of these two varieties is limited in sunflower hybrid breeding.