Molecular Analysis of S-haplotypes in Peach, a Self-compatible Prunus Species

The most commercially grown peach [ Prunus persica (L.) Batsch.] cultivars do not require cross-pollination for reasonable fruit set; however, self-incompatibility is a well-known feature within the Prunoideae subfamily. Isoelectric focusing and native polyacrylamide gel electrophoresis of S -ribonucleases; PCR analyses of S -RNase and S -haplotype-specific F-box genes as well as DNA sequencing were carried out to survey the self-(in)compatibility allele pool and to uncover the nature of self-compatibility in peach. From 25 cultivars and hybrids with considerable diversity in phenotype and origin, only two S -haplotypes were detected. Allele identity could be checked by exact length determination of the PCR-amplified fragments and/or partial sequencing of the peach S 1 -, S 2 -, and Prunus davidiana (Carr.) Franch. S 1 -RNases. S -RNases of peach were detected to possess ribonuclease activity, and a single nucleotide polymorphism in the S 1 -RNase was shown, which represents a synonymous substitution and does not change the amino acid present at the position in the protein. A 700-bp fragment of the peach SFB gene was PCR-amplified, which is similar to the fragment size of functional Prunus L. SFBs. All data obtained in this study may support the contribution of genes outside the S -locus to the self-compatible phenotype of peaches.