Cytogenetic studies on natural intergeneric hybridization inAster alliances |
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Authors: | Masanobu Tara |
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Institution: | (1) Department of Science Education, Faculty of Education, Okayama University, Tsushima-Naka, 3-1-1, 700 Okayama |
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Abstract: | The karyotype and meiosis of the 12-ploid plants—one of the offspring of the natural F1 hybrid (Aster ageratoides subsp.ovatus (2n=36) ×Kalimeris incisa (2n=72), 2n=72)—were examined. The 2n=108 chromosomes of the 12-ploids were found to consist of 18 large chromosomes and
90 small chromosomes. In meiosis of the PMCs of the 12-ploid, chromosome configurations of 3III+46II+7I, 2III+48II+6I and 3III+47II+5I were observed. All the univalents and trivalents were small, and among the 46–48 bivalents nine were large and the remaining
37–39 were comparatively small. The large bivalents were found to represent autosyndetic pairings, and the small bivalents
and trivalents were probably formed by autosyndetic pairings. The large chromosomes of the 12-ploids were found to coincide
with the large chromosomes ofovatus, and the 90 small chromosomes to correspond to small chromosomes ofovatus andK. incisa. The 12-ploids were concluded to have been produced by a fusion of an unreduced gamete of the F1 plant and a reduced gamete ofK. incisa which was growing in proximity to the F1s. Thus the 12-ploids were regarded to be an amphidiploid having 36 chromosomes ofovatus and 72 chromosomes ofK. incisa. |
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