Study on mechanism of obtaining genetic diversity in agaposermous plants

无配子生殖是指在配子不受精的情况下产生新的后代个体的生殖系统。在植物中，除了营养繁殖外，还经常发现无配子生殖。在无配子生殖中，既不发生多样化，也不发生遗传变化，因为它们与母体植物是同一个克隆。因此，它被称为进化的死胡同。然而，大量的遗传变异往往存在于无配子体植物群体中。本研究以菊科蒲公英属（Taraxacum）和苦碟子属（Ixeris dentata complex）两个属为研究对象，探讨了无配子体植物遗传多样性的形成机制。本研究通过对蒲公英属和Ixer属的有性群体和无性群体的染色体数目进行分析，探讨了蒲公英属和Ixer属无性群体遗传多样性的形成机制 关于我们 主要介绍了二倍体有性种、三倍体和四倍体无花受精种的野生居群遗传分析、杂交试验、生态生理特性。在这两个属中，观察到的野生种群的遗传变异。特别是苦碟子属植物，种群中绝大多数个体的基因型不同，这与前人的研究结果相一致。为了阐明产生遗传多态性的机制，进行了三倍体无性种与二倍体有性种、二倍体有性种与假定杂种以及两属中三倍体无性种个体之间的杂交试验。结果，在所检查的每个组合中获得杂种。进一步对杂交获得的种子进行了DNA含量分析。结果表明，F_1杂种与二倍体或其它杂种个体杂交的证据。少

Agamospermy is a reproductive system that produces a new descendant individual without fertilization of the gametes. In plants, agamospermy is often found in addition to vegetative reproduction. In agamospermy, neither the diversification nor the genetic changes take place because they are the same clone to their mother plant. Thus, it was said as the blind alley of evolution. However, large amount of the genetic variation are often found in agamospermous plant population. The purpose of this study is to clarify the mechanism that agamospermous species acquires genetic diversity by using two genera of Asteraceae, Taraxacum (hybridization between the Japan diploid dandelions and T.officinale) and Ixeris (Ixeris dentata complex). In this study, agamospermous and sexual population was analyzed in chromosome number, the genetic variation were examined for the purpose of clarification of mechanisms to obtain genetic diversity in agamospermous species.In the populations of Taraxacum and Ixer … More is, the genetic analyses of wild populations, crossing experiments, ecological and physiological characteristics in diploid sexual species, and triploid and tetraploid agamospermous species. In both genera, genetic variation was observed in the wild population examined. Especially in the Ixeris, most individuals in the population were found to be having different genotype one another, and it was concordant with previous studies. To clarify a mechanism to produce genetic polymorphism, crossing experiments was done between individuals of triploid asexual species and diploid sexual species, diploid sexual species and presumed hybrids, and the individuals of triploid asexual species in both genera. As a result, hybrids were obtained in every combination examined. The seeds obtained by crossing experiment were analyzed further, for DNA content with a flow cytometer were done in Taraxacum. As a result, the evidence that the F1 hybrids had been crossing with the diploids or the other hybrid individual was obtained. Less