Clonality in wild rice (Oryza rufipogon, Poaceae) and its implications for conservation management

Correlations were examined between habitat characters and clonal structures determined by the RAPD (random amplified polymorphic DNA) assay in five populations of Oryza rufipogon in China. Nine of 175 decameric primers were used in the study because they reproducibly amplified polymorphisms. The extent of clonality together with the clonal and sexual reproductive strategies varied greatly among the five populations and correlated with the habitats where they occur. The populations under serious disturbance or seasonal drought tended to have small clones with relatively high clonal diversity caused by sexual reproduction, whereas the populations with little disturbance and sufficient supply of water were prone to have large clones with relatively low clonal variation and low sexual reproduction. Therefore, the dynamics of sexual vs. clonal reproduction of this species depended mainly on environmental factors, such as external disturbance and water supply, rather than latitudes indicated by previous study. These results have important implications for in situ conservation of O. rufipogon. Adequate external disturbance and water supply control are essential for maintaining high clone diversity of in situ conserved populations. According to the extent of clonality of the populations examined, we recommend that an interval of >12 m should be required for collecting samples for ex situ conservation and for population genetic studies to capture possible genetic diversity for O. rufipogon in China.