A segmental duplication encompassingS-haplotype triggers pollen-part self-compatibility in Japanese pear (Pyrus pyrifolia).
Self-compatible mutants of self-incompatible crops have been extensively studied for research and agricultural purposes. Until now, the only known pollen-part self-compatible mutants in Rosaceae subtribe Pyrinae, which contains many important fruit trees, were polyploid. This study revealed that the pollen-part self-compatibility of breeding selection 415-1, a recently discovered mutant of Japanese pear (Pyrus pyrifolia) derived from γ-irradiated pollen, is caused by a duplication of anS-haplotype. In the progeny of 415-1, some plants had threeS-haplotypes, two of which were from the pollen parent. Thus, 415-1 was able to produce pollen with twoS-haplotypes, even though it was found to be diploid: the relative nuclear DNA content measured by flow cytometry showed no significant difference from that of a diploid cultivar. Inheritance patterns of simple sequence repeat (SSR) alleles in the same linkage group as theS-locus (LG 17) showed that some SSRs closely linked toS-haplotypes were duplicated in progeny containing the duplicatedS-haplotype. These results indicate that the pollen-part self-compatibility of 415-1 is not caused by a mutation of pollenSfactors in either one of theS-haplotypes, but by a segmental duplication encompassing theS-haplotype. Consequently, 415-1 can produceS-heteroallelic pollen grains that are capable of breaking down self-incompatibility (SI) by competitive interaction between the two differentSfactors in the pollen grain. 415-1 is the first diploid pollen-part self-compatible mutant with a duplicatedS-haplotype to be discovered in the Pyrinae. The fact that 415-1 is not polyploid makes it particularly valuable for further studies of SI mechanisms.
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan ; Graduate School of Life and Environmental Science, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572 Japan.
Nobuko
N
Mase
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan.
Yutaka
Y
Sawamura
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan ; Graduate School of Life and Environmental Science, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572 Japan.
Toshiya
T
Yamamoto
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan.
Norio
N
Takada
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan.
Sogo
S
Nishio
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan.
Toshihiro
T
Saito
NARO Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605 Japan ; Graduate School of Life and Environmental Science, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572 Japan.
Hiroyuki
H
Iketani
Competitive interaction; Pollen-part self-compatible mutant; Pyrus pyrifolia; Segmental duplication; Self-incompatibility; γ-Irradiation