Two novel self-compatible S haplotypes in peach (Prunus persica)
2014
Hanada, T. (Kyoto University, Kyoto (Japan). Graduate School of Agriculture) | Watari, A. | Kibe, T. | Yamane, H. | Wünsch, A. | Gradziel, T.M. | Sasabe, Y. | Yaegaki, H. | Yamaguchi, M. | Tao, R.
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, Ssup(1), Ssup(2), and Ssup(2m), that confer self-compatibility on commercial peach cultivars for fruit production. In this report, we identified 2 novel SC S haplotypes, Ssup(3) and Ssup(4), among 130 peach cultivars and strains consisting mainly of ornamental cultivars and wild strains. The Ssup(3) haplotype was found only in ornamental cultivars, while the Ssup(4) haplotype was found mainly in wild strains. S-RNases in the Ssup(3) and Ssup(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 Ssup(3)- and Ssup(4)-RNases. These SFB sequences were in a reverse transcriptional orientation as has been reported in most other functional Prunus S haplotypes; however, both SFBsup(3) and SFBsup(4) appeared to be mutated. DNA sequencing of the entire downstream region of SFBsup(3), extending about 12 kbp to the stop codon of S-RNase, revealed the presence of a premature stop codon 975 bp downstream from the SFBsup(3) start codon. No sequence homologous to SFB downstream of the stop codon was found. There was a 4946 bp insertion in the middle of SFBsup(4). The original SFBsup(4) sequence, obtained by removing the inserted sequence, encodes a typical SFB. Based on the 3 previously identified peach S haplotypes, we supposed that the Ssup(3) and Ssup(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.
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