Molecular Basis of Self-(in)compatibility and Current Status of S-genotyping in Rosaceous Fruit Trees

Most rosaceous fruit tree species exhibit gametophytic self-incompatibility (GSI). During the last decade, much progress has been made in identifying and characterizing the S-locus genes that control the specificity of the self-incompatible (SI) reaction in the Rosaceae. The pistil and pollen determinants of S-specificity in the Rosaceae are a ribonuclease and an F-box protein, respectively. From allele-specific sequence polymorphism of S-specificity genes, molecular S-genotyping systems have been established in various rosaceous fruit tree species. Molecular characterization of S-determinants in self-compatible (SC) cultivars has revealed defects in the S-determinants that cause SC and enabled the development of molecular markers for SC. Marker-assisted selection of SC offspring is now being successfully incorporated into breeding programs. In this paper, we summarize the current knowledge of the molecular basis of self-(in)compatibility, S-genotyping methods, and molecular markers for SC in rosaceous fruit tree species.