Identification of quantitative trait loci associated with self-compatibility in a Prunus species
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Self-compatibility in Rosaceous fruit species is based on a single-locus qualitative trait. However, the evidence observed in different species has indicated the presence of modifier genes outside the S locus affecting the expression of self-compatibility/self-incompatibility. The study of a progeny obtained from the cross of the almond genotypes ‘Vivot’× ‘Blanquerna’ has allowed the construction of a genetic map based on microsatellite markers and the identification for the first time in the Rosaceae family of two additional loci located outside the S locus and affecting the expression of self-compatibility/self-incompatibility. A quantitative trait locus (QTL) was located relatively close to the S locus, on linkage group 6 (G6), whereas the second one was located on G8. These QTLs appear to be involved in conferring self-compatibility to genotypes not possessing the Sf allele. These results are consistent with almond being a self-incompatible species with a genetic background of pseudo-self-compatibility controlled by modifier genes. The effect of the Sf allele and the two QTLs may contribute to explain the wide range of fruit sets observed when self-pollinating different almond genotypes.