Abstract
An amphidiploid cultivar of Camellia, 'Fragrant Plnk Imoroved syntheslzed by colchicine treatment from a di.ploid intersectional hybrid between a diploid clone of C.japoleica subsp. rustical (Honda) Kitamura and of C. Iu.tchuelesis T. Ito named 'Fragrant Pink' was studied to clarify genomic affilnity between species of Caleeellia. The majority of the pollen mother cells of 'Frag'rant Pink Improved' studied showed the predominant fcrmation of bivalents and high chiasma frequency except for a few univalents and multivalents at metaphase I in meiosis and rather high pollen viability with a mean of 77 percent. The diploid parental clones of the F1 hybrid 'Fragrnta Pink' showed complete and normal 15 bivalent chromosomes at metaphase I in meiosis of pollen mother cells and high pollen viability, while 'Fragrant Pink' showed a single chromosome configulatlon of 15 bivalents and the chrasma frequency deviated only slightly from those of the parents, but very low pollen viability with a mean of four percent. Thus, each pair of partially homologous chromosomes from Calaeelliajaponica subsp. rusticana and that from C. Iutchuensis include different degree of homologous segrnents. Either cryptic structural differences or differences of the gene constitution without any chromosollrlal structural differences would be expected between the chro-mosomes of C.japoleica subsp. rusticana and of C. Iutchuensis. During the course of investigaton, two percent of the pollen mother cells of amph, idiploid 'Fragrant Pink Improved' showed complete and normal 15 bivalent chromosomes at metaphase I in meiosis. The presence of partial pollen sterility shown in the amphidiploid clone of 'Fragrant Pink Improved' might be due to both unstable meiotic chrornosome configurations at metaphase I and unusual nuclear divisions in meiosis in pollen mother cells, especially cytomixis.
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