Study on mechanism of obtaining genetic diversity in agaposermous plants

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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