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Keywords:

  • Oryza rufipogon;
  • O. sativa;
  • pollen competition;
  • sequential pollination;
  • reproductive isolation

Summary

  •  Post-pollination competition is reported here in cultivated rice (Oryza sativa) and a perennial wild rice (O. rufipogon) to investigate the occurrence of crop-to-wild gene flow.
  •  Wild and cultivated rice (variety Minghui-63) were grown in a common garden in Hunan province, China, and crop-specific genetic markers were used to detect hybridization following hand-pollinations. Using 11 sequential pollination treatments, the effects of the relative timing of pollination on the success of foreign pollen was investigated.
  •  Foreign pollen from the crop resulted in lower pollen germination, fewer pollen tubes per style, and a significant reduction of seed set, demonstrating a disadvantage of foreign pollen even in the absence of pollen competition. When 1 : 1 pollen mixtures were applied, only 2% of the resulting seeds were hybrids, revealing a much stronger disadvantage of foreign pollen when competing with conspecific pollen. Testing the effects of the relative timing of pollination on the success of foreign pollen suggested that conspecific pollen is often more successful than foreign pollen. Nonetheless, hybridization is possible following the deposition of pollen mixtures, especially when foreign pollen arrives earlier than conspecific pollen.
  •  Pollen competition between wild and cultivated rice could slow the rate of crop-to-wild gene flow, but even if pollen competition was ubiquitous it would not prevent gene flow from the crop.