Abstract
Since a pre-zygotic isolating mechanism has been shown to be functioning completely between Group II-B plus and Group II-A minus (Watanabe and Ichimura, 1978b), the reciprocal cross was investigated in order to clarify the presence of a postzygotic isolating mechanism between the two sympatric closely related groups of theClosterium peracerosum-strigosum-littorale complex. Viabilities and fertilities of F1, F2 and backcross progenies of crosses within and between the two groups were studied using two representative pairs, IB-4-2 and IB-4-9 of Group II-A and KAS-4-30 and KAS-4-29 of Group II-B. Viability was estimated by % survival of isolated gones. Viability of F1 progeny was 31.7% in the intergroup cross, while it was 70.0 and 46.0% in the intragroup cross of Group II-A and that of Group II-B, respectively. Viabilities of intragroup F2 and backcross progenies were shown to be in the range of 32.0–76.0%. In contrast with this, those of F2 and backcross progenies of the hybrids obtained in the intergroup cross were shown to be markedly reduced to the range of 0.0–2.5%.
Viable clones obtained in these intra-and intergroup crosses were almost all fertile, but one sterile clone was fonnd among F1 progeny of Group II-B. It was concluded that the so-called hybrid breakdown is also at work as, an isolating mechanism between the two groups of this complex.
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This study was supported by the Grants in Aid. Nos. 00554220 and 56122019, from the Scientific Research Found of the Ministry of Education, Science and Culture, Japan.
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Watanabe, M.M., Ichimura, T. Biosystematic studies of theClosterium peracerosum-strigosum-littorale complex IV. Hybrid breakdown between two closely related groups, group II-A and group II-B. Bot Mag Tokyo 95, 241–247 (1982). https://doi.org/10.1007/BF02488536
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DOI: https://doi.org/10.1007/BF02488536