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

对三种荞麦（Fagopyrum）在世界各地的分布进行了调查，分别在普通荞麦、苦荞和多年生荞麦中收集了148份、88份和29份样品。等位酶变异的电泳测定和这些样品的形态特征的比较分析得出以下结论。(1)栽培荞麦群体的同工酶变异比其他异交植物物种的平均变异要大得多。中国南部和印度东部的种群变异最大；这个区域可能是变异的中心。然而，没有检测到等位酶频率的关键地理分化；只有在分布的边缘，即印度和南欧的库曼和克什米尔，才发现了微小的差别。等位酶频率和形态特征的均匀性可能与种群规模大、交配次数少、种群间基因流动充足有关。荞麦栽培的传播过程可以从地理变化或同工酶的丧失中看到痕迹。(2)来自喜马拉雅地区、中国和欧洲的其他栽培荞麦品种鞑利荞麦的形态差异很大，但它们在同工酶上的差异有限，这与我们根据该品种自花传粉的性质所期望的种群间差异很大相矛盾。目前对此没有合理的解释。(3)中国多年生荞麦为二倍体，而泰国、印度和尼泊尔多年生荞麦为四倍体。自然种群主要靠植物繁殖。然而，天然群体的等位酶变异性与普通荞麦一样多，表明种子繁殖在维持变异性方面起着重要作用。因此，对三种荞麦的等位酶数量和形态变异进行了评估，并部分了解了维持这些变异的机制。明确了荞麦栽培的变异区、局部分化区和推广过程。少

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