Comparative study of rbcL gene sequences in Fagopyrum and related taxa.

Four species of Fagopyrum, two species of Persicaria and one species of Rumex were analyzed for the DNA sequences of their rbcL genes. In addition to these seven species, we analyzed the published or available sequence data of ten related taxa in Polygonales, Plumbaginales and Caryophyllales. By estimating the base substitution rate between each pair of species, and by constructing phylogenetic trees we concluded that: 1) In Fagopyrum, F. cymosum and F. tataricum are much more closely related than expected previously; this confirms the conclusion of Kishima et al. (1995). 2) The new classification of Fagopyrum species proposed by Ohnishi and Matsuoka (1996) based on morphology, isozyme and cpDNA variability is consistent with the rbcL sequences. 3) The Polygonales and the Plumbaginales should be separated from the Caryophyllales as concluded by Giannasi et al. (1992). 4) The separation of Fagopyrum from other genera in the Polygoneae has a solid molecular basis.