Two Novel Self-compatible S Haplotypes in Peach (Prunus persica)

摘要

Peach (Prunus persica) as a species is self-compatible, (SC), although most other Prunus fruit tree species are partially or fully self-incompatible. We previously identified 3 mutated S haplotypes, S-1, S-2, and S-2m, that confer self-compatibility on commercial peach cultivars for fruit production. In this report, we identified 2 novel SC S haplotypes, S-3 and S-4, among 130 peach cultivars and strains consisting mainly of ornamental cultivars and wild strains. The S-3 haplotype was found only in ornamental cultivars, while the S-4 haplotype was found mainly in wild strains. S-RNases in the S-3 and S-4 haplotypes appeared to have no defects in their primary structures. S haplotype-specific F-box (SFB) sequences were also present in the S locus downstream of the S-3- and S-4-RNases. These SFB sequences were in a reverse transcriptional orientation as has been reported in most other functional Prunus S haplotypes; however, both SFB3 and SFB4 appeared to be mutated. DNA sequencing of the entire downstream region of SFB3, extending about 12 kbp to the stop codon of S-RNase, revealed the presence of a premature stop codon 975 bp downstream from the SFB3 start codon. No sequence homologous to SFB downstream of the stop codon was found. There was a 4946 bp insertion in the middle of SFB4. The original SFB4 sequence, obtained by removing the inserted sequence, encodes a typical SFB. Based on the 3 previously identified peach S haplotypes, we supposed that the S-3 and S-4 haplotypes were also SC pollen part mutant (PPM) S haplotypes. Here, we also discuss possible reasons for all peach S haplotypes identified so far having the PPM SC S haplotype.