Study of self-compatibility in almond progenies from self-fertilization by fluorescence microscopy and stylar ribonuclease assay

Self-incompatibility in almond is gametophytic and controlled by a single S-locus with several codominant alleles encoding for specific ribonucleases and a dominant self-fertility allele (Sf) that does not encode for ribonuclease activity. In most studies of inheritance of self-compatibility, crosses between self-compatible and self-incompatible cultivars were studied. However, progenies from self-pollination are scarce. In this work, self-compatibility of 214 seedlings from self-pollination of 30 self-compatible selections, obtained by the CEBAS Almond Breeding Programme, was studied by means of fluorescence microscopy and stylar ribonuclease assay. Results showed that self-fertilization of self-compatible genotypes guarantees self-compatibility in the offspring and allows homozygous individuals for the Sf allele to be obtained. Both methods are reliable for assessing self-compatibility in this species. Furthermore, stylar ribonuclease assay allowed the determination of the S genotype in the progeny and detected some unexpected S-genotypes.