Genetic differentiation in three buckwheat(Fagopyrum) species with the distinct reproductive systems and the origin of cultivated buckwheat species

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A world-wide survey of the distribution of three buckwheat(Fagopyrum) spcies was conducted and 148, 88 and 29 samples were collected in common buckwheat, tatary buckwheat and perennial buckwheat, respectively, from various parts of the world. Electrophoretic assay of allozyme variability and a comparative analysis of morphological traits on these samples led to the following remarks.(1) Cultivated populations of common buckwheatmaintain much more allozyme variability in a population than the average of other outcrossing plant species. The populations from southern China and eastern India had most variability; this area may be the center of variability. However, no crucial geographical differentiation of allozyme fequencies was detected; minor differentiations were found only at the margins of distribution, i.e. Kumaun and Kashmir in India and southern Europe. The observed uniformity of allozyme frequencies and morphological traitsmay be interpreted by large population sized and randomn … More ess of mating along with the sufficient gene flow between populations. The traces of the spreading processes of buckwheat cultivation could be seen in the geographical changes or losses of allozymes.(2) The samples of tatary buckwheat, the other cultivated bucukwheat species, from the Himalayan region, China and Europe were quite variable in morphology, yet they showed limitted differences in allozymes, in contradiction to our expectation of great variability between populations from the nature of self-pollination of this species. At present, no reasonable interpreation is available for this.(3) The perennial buckwheat samples from China were revealed to be diploid, while those distributed in Thailand, India and Nepal were tetraploid. The natural populations are predominantly reproduced vegetatively. However, the natural populations had as much allozyme variability as common buckwheat, indicating that seed reproduction plays an important role in maintenance of variability.Thus, the amount of allozyme and morphological variability was assessed for three buckwheat species, and the mechanisms that maintain those variability were partly understood. The variability-rich regions, the area where local differentiation took places, and the spreading processes of buckwheat cultivation have been clarified. Less