Dual recognition of S 1 and S 4 pistils by S 4 sm pollen in self-incompatibility of Japanese pear (Pyrus pyrifolia Nakai)
2012
Saito, Toshihiro | Sato, Yoshihiko | Sawamura, Yutaka | Shoda, Moriyuki | Takasaki-Yasuda, Takeshi | Kotobuki, Kazuo
Most cultivars of Japanese pear (Pyrus pyrifolia Nakai) exhibit gametophytic self-incompatibility controlled by a single S-locus with multiple S-haplotypes. A self-compatible (SC) cultivar, ‘Osanijisseiki’ (S 2 S 4 sm ), arising by a bud mutation of ‘Nijisseiki’ (S 2 S 4 ), has a stylar-part mutant S 4 sm -haplotype, which lacks the pistil S 4 gene, which is the S 4 -RNase gene. To efficiently breed SC cultivars, we selected ‘Nashi Chuukanbohon Nou 1 Gou’ (‘NCN1’) harboring homozygous S 4 sm from a self-progeny of Osanijisseiki and crossed it with ‘Okusankichi’ (S 5 S 7 ), ‘Hakkou’ (S 4 S 5 ), or ‘Ri-14’ (S 1 S 2 ). Fruit set (%) was compared after self-pollination of the trees in the three progenies. All trees derived from the three progenies were predicted to be SC, except for the S 4 S 4 sm trees in the progeny of NCN1 × Hakkou. However, S 1 S 4 sm trees in the progeny of NCN1 × Ri-14 proved to be self-incompatible (SI). The pollen from Osanijisseiki was incompatible with ‘Doitsu’ (S 1 S 2 ), but that from Nijisseiki was compatible, suggesting a possibility that the S 4 sm pollen was rejected by S 1 -harboring pistils. This possibility was clarified by crossing the pollen from NCN1 (S 4 sm S 4 sm ) to Doitsu, ‘Imamuraaki’ (S 1 S 6 ), or ‘Hougetsu’ (S 1 S 7 ), all of which proved incompatible. On the other hand, S 4 sm pollen was accepted by pistils harboring the S 2 , S 3 , S 5 , S 6 , S 7 , S 9 , and S k haplotypes. The dual recognition of S 1 and S 4 pistils by S 4 sm pollen can be attributed to a mutation of the pollen S 4 gene(s).
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