Hybridizations involving different species are often hindered because of incompatibility reactions. Although these reproductive barriers have been observed in many plant species, the underlying mechanisms remain to be comprehensively elucidated. In this study, we detected a hybridization barrier between apple (Malus × domestica) and pear (Pyrus spp.) belonging to different genera in the subtribe Malinae of the family Rosaceae. Pollination experiments revealed that Pyrus pyrifolia (Japanese pear) pollen is compatible with Malus pistils, whereas Pyrus communis (European pear) pollen is not. These results imply there is a distinct cross-(in)compatibility reaction occurring in Pyrus species. Based on the varying pollen tube behaviors among Pyrus species, genetic analysis was conducted to identify the genomic region responsible for the intergeneric barrier. Malus–Pyrus intergeneric hybrids were used to detect distorted segregation regions by combining genome sequencing and fine-scale genotyping data. We defined a single locus on chromosome 5, in which P. pyrifolia-derived alleles were exclusively inherited to the intergeneric hybrids from the Pyrus interspecific hybrid. Of the 235 genes in this genomic region, 80 exhibited a specific pollen-expression pattern, including genes involved in self-incompatibility reactions. These candidate genes are herein discussed regarding their possible functions related to reproductive isolation.
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Data archiving statement
The datasets generated during the current study are available in the DDBJ SRA (Sequence Read Archive), under the BioProject number PRJDB8418.
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We appreciate the valuable comments and suggestions provided by Dr. Fabrizio Costa regarding the manuscript. We also thank Ms. Rieko Ishida and Mr. Yutaro Osako for maintaining plants during experiments.
This work was supported by the Overseas Research Fellowship provided by the Japan Society for the Promotion of Science (JSPS) to T.M. (201860070 and 19K15834). This study received financial assistance from the authors Drs Ryutaro Tao and Takashi Akagi [JSPS Grants-in-Aids for Scientific Research (A) (No. 15H02431) to RT and for Challenging Exploratory Research (No. 17K19265) to TA].
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Morimoto, T., Inaoka, M., Banno, K. et al. Genetic mapping of a locus controlling the intergeneric hybridization barrier between apple and pear. Tree Genetics & Genomes 16, 5 (2020). https://doi.org/10.1007/s11295-019-1397-7
- Intergeneric hybridization
- Pollen tube growth
- Reproductive isolation
- Segregation distortion