Abstract
The majority of the cultivated species and cultivars of hexaploid Camellia studied showed complete and normal pairing at metaphase I in meiosis, while their hybrids showed various meiotic chromosome configurations and chiasma frequencies at metaphase I. Thus, the predominant formation of bivalents and the high chiasma frequency per bivalent at metaphase I in meiosis shown in the population of hexaploid clones of cultivated Camellia taxa might be due to stable, fertile combinations derived from allohexaploids and segmental allohexaploids in which a large amount of homologous segments might be distributed throughout the genomes. Since such heterozygous chromosome complexes are carried in the hexaploid Caleeellia taxa, no distinct dividing line could be found between so-called homologous and non-homologous genomes, and one genome might merge into the others. Observations on metaphase chromosome pairing in meiosis I in hybrids between hexaploid Camellia taxa have stressed the difficulty of making genome formulas and drawing phylogenetic relationships of Camellia taxa. The presence of sterility and partial sterility shown in hexaploid Camellia taxa and their hybrids might be due to both genetic and chromosomal differences as well as de-veloping petaloidy.
