CHLOROPLAST DNA ANALYSIS IN BUCKWHEAT SPECIES - PHYLOGENETIC-RELATIONSHIPS, ORIGIN OF THE REPRODUCTIVE SYSTEMS AND EXTENDED INVERTED REPEATS

We have constructed physical maps for the chloroplast genomes of buckw heat (Fagopyrum esculentum) and related species (F. tataricum and F. c ymosum) 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. Phylog enetically, 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 reproduc tive system for Fagopyrum, whose present-day species display three dif ferent mechanisms of reproduction: allogamous, autogamous and vegetati ve, because both the distantly related species, F. esculentum and F. c ymosum, maintain self-incompatibility due to heterostyly. We also obse rved that the unique 5.05-kb Sma-8 fragments, which extend the inverte d repeats in buckwheat species, exhibit little homology with tobacco c hloroplast DNA clones.