Study on mechanism of obtaining genetic diversity in agaposermous plants

无精卵是一种生殖系统，它在没有配子受精的情况下产生新的后代个体。在植物中，无性生殖除了营养繁殖外，还经常被发现。在无性生殖中，既不会发生多样性，也不会发生遗传变化，因为它们是与母体植物相同的克隆。因此，它被称为进化的死胡同。然而，在无子植物种群中经常发现大量的遗传变异。本研究旨在阐明菊科植物蒲公英(日本二倍体蒲公英与药用蒲公英杂交)和Ixeris(Ixeris dentata复合体)两个属植物获得遗传多样性的机制。本研究对无精子植物和有性种群的染色体数目进行了分析，并对其遗传变异进行了分析，旨在阐明获得无精子植物遗传多样性的机制。在蒲公英和Ixer…的种群中此外，还对野生种群的遗传分析、杂交试验、二倍体有性种、三倍体和四倍体无精子植物的生态生理特性进行了综述。在所研究的野生种群中，这两个属都观察到了遗传变异。特别是在Ixeris群体中，发现群体中的大多数个体具有不同的基因型别，这与以往的研究是一致的。为了阐明遗传多态产生的机理，对三倍体无性种与二倍体有性种、二倍体有性种与推定杂交种的个体与三倍体无性种的个体进行了杂交试验。结果，在所检测的每个组合中都获得了杂交后代。对杂交获得的种子进行进一步分析，用流式细胞仪对蒲公英进行DNA含量测定。因此，获得了F_1代与二倍体或其他杂种个体杂交的证据。较少

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