In Brassicaceae, self-incompatible plants have a self/non-self recognition system, which involves the inability of flowering plants to achieve self-fertilisation. This is sporophytically controlled by multiple alleles at a single locus (S). There are a total of 50 different S alleles in Brassica oleracea. S-locus glycoproteins, as well as S-receptor kinases, are in linkage with the S-alleles. Most of the proteins within this family contain apple-like domain , which is predicted to possess protein- and/or carbohydrate-binding functions.