Self-fertility is largely decreased and even prevented by various mechanisms because, broadly, it causes inbreeding depression, although some species have retained self-reproduction regimes. Species of plants that display the self-incompatible sporophytic type of self-incompatibility may rarely self-pollinate. It is only possible in the absence of foreign compatible pollen. In the olive tree with a sporophytic mechanism, we will show that three co-dominant S-alleles R1, R3 and R5 do not lead to the same level of self-fertility. All varieties that carry R1 are less self-fertile than those that carry R5, whatever the other S-alleles, while those carrying R3 are intermediate. S-allele pair-wise combinations that differ by two or three levels of dominance, and not the other combinations allow self-fertility, and moreover each S-allele R1, R3 and R5 decreases, maintains and enhances the self-fertility rate, respectively.