Chloroplast DNA analysis in buckwheat species: phylogenetic relationships, origin of the reproductive systems and extended inverted repeats

Abstract

We have constructed physical maps for the chloroplast genomes of buckwheat ( Fagopyrum esculentum) and related species ( F. tataricum and F. cymosum) by using six restriction enzymes. The genome sizes were found to be identical with approximately 155.5 kb. A comparison of physical maps revealed 11 altered restriction sites out of 259 analyzed. Phylogenetically, the chloroplast DNA of F. esculentum has been found to be quite distant from those of F. tataricum and F. cymosum. These results also suggest that the allogamous mode could be the ancestral reproductive system for Fagopyrum, whose present-day species display three different mechanisms of reproduction: allogamous, autogamous and vegetative, because both the distantly related species, F. esculentum and F. cymosum, maintain self-incompatibility due to heterostyly. We also observed that the unique 5.05-kb Sma-8 fragments, which extend the inverted repeats in buckwheat species, exhibit little homology with tobacco chloroplast DNA clones.