Quiescence in rice submergence tolerance: an evolutionary hypothesis.

Rice (Oryza sativa) varieties differ considerably in their tolerance to submergence, a trait that has been associated with the SUB1A gene. Recently, this gene was found in some wild rice species and landraces, which along with O. sativa, belong to the AA genome type group. On the basis of geographical and historical data, we hypothesize that SUB1A-1 from wild species may have been introgressed into domesticated rice. This introgression probably occurred in the Ganges Basin, with the subsequent spread of the SUB1A-1 to other areas of South Asia due to human migration. The lack of the SUB1A gene in diploid CC genome type wild rice showing submergence-tolerant traits suggests the presence of a different survival mechanism in this genetic group.