Gametophytic incompatibility in pome and stone fruits: genes controlling S-locus.

Angiosperms are the most prevalent and evolutionarily advanced group of plants. A critical step for the success of flowering plants was the wide promotion of cross-fertilization as reproductive strategy. The Gametophytic Self-Incompatibility (GSI) system represents one of these strategies and it occurs in Rosaceous species (i.e. pome and stone fruits). Self-incompatibility is determined by haplotypes of the S-locus; the pistil specificity is controlled by an S locus-encoded ribonuclease (SRNase) and the pollen determinant is a protein containing an F-box domain (SFbox). S-RNases have been very well characterised thanks to the “genotyping of Salleles” (S-genotyping): this approach supported the definition of the inter-fertility groups among varieties of species in which self-incompatibility is diffused and allowed the identification of mutated alleles that occasionally result in self-fertile genotypes. In this paper all these aspects will be taken into account as well as the evolutionary differentiation of GSI in the Prunoideae (i.e. Prunus) with respect to the Pyrinae (i.e. Malus and Pyrus), that produced different S-locus structures and features in the two taxa; the roles of the pistil S and pollen S mutants in GSI breakdown and the possibility to overcome self-incompatibility by genetic engineering approach will be discussed.