The origin of the self-compatible almond 'Supernova'

The almond cultivar 'Supernova' is reported in the literature as a late-flowering self-compatible mutant, obtained by the irradiation of the early-flowering self-incompatible cultivar 'Fascionello'. Our work to investigate the molecular basis of this form of self-compatibility has called into question the origin of 'Supernova'. Test selfing was performed both on 'Supernova' and on the accession of 'Fascionello' from which it was derived –'Fascionello-Rome'. Both proved self-compatible. Amplification of S - RNase alleles, using consensus primers from the signal peptide region to the second conserved region of the S - RNase gene and primers specific for allele S _f , confirmed 'Supernova' and 'Fascionello-Rome' indeed have the same (in)compatibility genotype S ₁ S _f as the self-compatible cultivar 'Tuono'. Nine microsatellite markers were used to fingerprint the relevant accessions; 'Supernova' and 'Fascionello-Rome' were undistinguishable from 'Tuono'. Two Sicilian accessions, 'Fascionello' and 'Falso Fascionello', lacked S _f and differed at the SSR level, indicating no close relationship with 'Supernova'. Therefore we concluded that 'Fascionello-Rome' is actually the same as 'Tuono' and that 'Supernova' originates from 'Tuono' from which it derives its self-compatibility.