In F1 hybrids of Oryza sativa (Asian rice) and O. glaberrima (African rice), heterozygosity leads to a complete gamete abortion because of allelic conflict at each of the 13 hybrid sterility (HS) loci. We systematically produced 19 plants from the F1 hybrids of both the rice species by the anther culture (AC) method. Five of the 19 interspecific hybrid plants were fertile and able to produce seeds. Unlike ordinal doubled haploid plants resulting from AC, these regenerated plants showed various ploidy levels (diploid to pentaploid) and different zygosities (completely homozygous, completely heterozygous, and a combination). These properties were attributable to meiotic anomalies in the interspecific hybrid F1 plants. Examination of the genetic structures of the regenerated plants suggested meiotic non-reduction took place in the interspecific hybrid F1 plants. The centromeric regions in the regenerated plants revealed that the abnormal first and/or second divisions of meiosis, namely the first division restitution (FDR) and/or second division restitution (SDR), had occurred in the interspecific hybrid. Immunohistochemical observations also verified these phenomena. FDR and SDR occurrences at meiosis might strongly lead to the formation of diploid microspores. The results demonstrated that meiotic anomalies functioned as a reproductive barrier occurred before the HS genes acted in gamete of the interspecific hybrid. Although such meiotic anomalies are detrimental to pollen development, the early rescue of microspores carrying the diploid gamete resulted in the fertile regenerated plants. The five fertile plants carrying tetraploid genomes with heterozygous alleles of the HS loci produced fertile diploid pollens, implying that the diploid gametes circumvented the allelic conflicts at the HS loci. We also proposed how diploid male gametes avoid HS with the killer-protector model.

中文翻译：

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二倍体雄配子规避亚洲和非洲稻种之间的杂交不育

在水稻（亚洲稻）和非洲稻（非洲稻）的F1杂种中，杂合性导致完全的配子流产，因为这13个杂种不育（HS）基因座中的每一个均存在等位基因冲突。我们通过花药培养（AC）方法从两种水稻的F1杂种系统地生产了19株植物。19种种间杂种植物中有5种能育并能够产生种子。与AC产生的有序双倍单倍体植物不同，这些再生植物显示出不同的倍性水平（二倍体到五倍体）和不同的合子性（完全纯合，完全杂合以及组合）。这些特性归因于种间杂种F1植物的减数分裂异常。对再生植物的遗传结构的研究表明减数分裂非还原发生在种间杂种F1植物中。再生植物的着丝粒区域显示减数分裂的异常第一和/或第二分裂，即第一分裂恢复（FDR）和/或第二分裂恢复（SDR），已经发生在种间杂种中。免疫组织化学观察也证实了这些现象。减数分裂中FDR和SDR的发生可能强烈导致二倍体小孢子的形成。结果表明减数分裂异常作为生殖屏障发生在HS基因在种间杂种的配子中起作用之前。尽管此类减数分裂异常不利于花粉发育，携带二倍体配子的小孢子的早期抢救产生了可育的再生植物。携带四倍体基因组与HS基因座杂合等位基因的五株可育植物产生了可育的二倍体花粉，这表明二倍体配子规避了HS基因座上的等位基因冲突。我们还用杀手-保护子模型提出了二倍体雄配子如何避免HS的方法。