| Research Abstract |
The interspecific hybridization is useful tool in sweetclover breeding program in order to improve such as sweetclover weevil resistance, the most important insect pest. However, it is not so easy to obtain the desireble interspecific F_1 hybrids by various sexual isolation factors. The present studies were conducted to obtain more precise informations about the interspecific relationships among species of the genus Melilotus. The results obtained are summarized as follws:
1. Karyotype analysis: Karyotype of 9 species of the subgenus Eumelilotus and 10 species of the subgenus of Micromelilotus have been examined by using Giemsa stained techniques. The general appearance of Karyotype studied were almost agree with the results have been reported by KITA(1966), who had analysed karyotype by using Feulgen-stained techniques before. The morphology of satellited chromosomes were precisely investigated.
2. Cytological relationships among 8 species of the subgenus Eumelilotus: Cytological studie
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s among 8species Eumelilotus have been studied by SANO and KITA(1976) and reported that RT exist between M.alba and M.hirsuta, M.officinalis, M.polonica, and M.suaveolens(A-group), and another RT exist between M.alba and M.dentata, M.taurica, and M.wolgica(B-group). The f_1 hybrids among 4 species of A-group and among 3 species of B-group were normal in cytological relationships. The cytological relationship between A-group and B-group are unknown, because no F_1 hybrid have obtained. Therefor, it is not known whether two RT described above are the same origin or not. The 3 way crosses such as (a species of A-group x M.alba) x a species of B-group have been conducted, and revealed that the two RT are the same origin.
3. Cross-compatibility between M.officinalis and M.alba: Cross hybridization as many as posible have been carried out between M.officinalis and M.alba using many strains, and found new strains; M.officinalis Bdn. 62-13, P.197-1, P.198-1, P.200-1, and P.200-2 which are crossable with M.alba. it is clear that these 5 strains would be expected to be used as gene exchange strains for breeding programs.
4. Tissue culture: Twelve species including 68 strains of melilotus were studied for tissue culture, and inter and intra specific differences of callus induction and growth were examined. No plant has been regenerated in two kinds of regeneration medium. Less
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