The S alleles from 17 accessions of Lithuanian origin and 5 standard varieties of sweet cherry were determined using the polymerase chain reaction (PCR) method. Initially, DNA extracts were amplified with consensus primers that amplify across the first, the second, or both introns of the S-ribonuclease gene which shows a considerable length polymorphism. Because the size of PGR products in this amplification is often similar, all complicated accessions later were tested with allele-specific primers. Combinations of S alleles were identified in all the accessions studied. After the investigation, Lithuanian sweet cherries were assigned to ten different self-incompatibility groups. New combinations of S alleles were identified – S₁S₁₃ (‘Žemaičių juodoji’) and S₆S₁₆ (‘Jurga’, ‘Anta’). One additional incompatibility group was proposed.

Keywords: S-alleles, incompatibility genotypes, allele-specific primers, consensus primers, Prunus avium