Cytogenetic Studies of Nicotiama VI
On Three Hybrids between N. tabacum and Other Species
1955 Volume 68 Issue 810 Pages 358-362
Details
1955 Volume 68 Issue 810 Pages 358-362
The three species, N. trigonophylla, N. undulata and N. rustica were crossed reciprocally with N. tabacum. The crosses N. tabacum×N. trigonophylla, N. undulata×N. tabacum and N. tabacum (Odaruma) ×N. rustica (Afghanistan) gave some seeds, while no seeds were obtained from the three remaining crosses. No report on the hybrids N. tabacum×N. trigonophylla and N. undulata×N. tabacum or their reciprocal crosses has been published, so far as I know.
In external characters the F1 tabacum-trigonophylla, is somewhat smaller than N. tabacum, the leaf form is intermediate between those in the parents, and the flower colour is a pale red. F1 undulata-tabacum is more similar to N. tabacum than to N. undulata, but its flowers are pale yellowish red, showing an intermediate color between the two parents. The morphology of F1 tabacum-rustica agrees with that of Kostoff's description of the reciprocal hybrid (N. rustica ×N. tabacum). These three hybrids were all vigorous.
All the hybrids mentioned above, showed considerable irregularities in the meiotic behaviour of the FMC's. Polysporous PMC's were often observed, and the hybrids were completely sterile.
At first metaphase in F1 tabacum-trigonophylla, 0-11 bivalents, mostly 5-6, were counted. In F1 trigonophylla-tomentosa and F1 trigonophylla-tomentosiformis, Kostoff (1941-43) observed 2-10 and 0-8 bivalents, respectively. Accordingly, the chromosome conjugation in F1 tabacum-trigonophylla is assumed to be caused mostly by semihomologous chromosomes between the trigonophylla genome and the tomentosa subgenome, not the sylvestris subgenome, of N. tabacum. In F1 undulata-tabacum, 0-8 bivalents, mostly 3-5, were observed. In this hybrid the number of the bivalents is a little more than that of the chromosome conjugation in haploid tabacum or F1 sylvestris-tomentosiformis. Accordingly it is assumed that a few semihomologous chromosomes are present between the undulata genome and the two subgenomes of N. tabacum. In F1 tabacum-rustica, 1-10 bivalents (also multivalents) were formed at the first metaphase and some secondary associations were observed at first and second metaphases. Christoff (1928) and Trenovsky (1935) also observed a small number of bivalents in F1 rustica-tabacum, while Kostoff (1941-43) found many bivalents, as many as 5-24, in the same hybrid. The cause of there different results was not determined.
