Observations on Interspecific Hybridization Barriers Between Oryza sativa and O. brachyantha
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Abstract
Oryza sativa and O.brachyantha belong to AA and FF genomes in genus Oryza, respectively. The interspecific hybridization barrier limits the transfer of elite genes from O.brachyantha into O.sativa. By using technique of whole-mount eosin B-staining confocal laser scanning microscopy, the development of hybrid embryo and endosperm after crossing between O.sativa and O.brachyantha and embryo sac abortion process of interspecific hybrid F1were observed. The results showed that there was a high double-fertilization ratio of 82.93% appearing in the pollinated spikelets, but hybrid embryo ceased to develop and began to degenerate at the globular-shaped stage, meanwhile, free endosperm nuclei degenerated before forming cellular endosperm. It induced hybrid embryo abortion and the matured hybrid seed failed be produced. During the process of hybrid embryo sac development, hybrid megasporocyte finished meioses, but abnormal tetrad was formed which induced abnormal functional megaspores. Embryo sac was degenerated at the stage of mono-nucleate and two-nucleate embryo sac, therefore, no normal embryo sac was formed and hybrid was highly sterile.
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