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Meiotic Chromosomes of Cienfuegosia Species and Hybrids and Hampea Species (Malvaceae)
F. D. Wilson and P. A. Fryxell
Bulletin of the Torrey Botanical Club
Vol. 97, No. 6 (Nov. - Dec., 1970), pp. 367-376
Published by: Torrey Botanical Society
Stable URL: http://www.jstor.org/stable/2483857
Page Count: 10
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Chromosome numbers of 14 of the 24 recognized species of Cienfuegosia Cav. are reported, six of which are new. Numbers are also reported for four of the 17 recognized taxa of Hampea Schlecht., three of which are new. Chromosome-number data support the previous separation of the species of Cienfuegosia into two alliances, subgenus Articulata, of Afro-Arabian distribution, with n = 11, and subgenus Cienfuegosia, of largely American distribution, with n = 10. Chiasma frequencies in Cienfuegosia vary from 1.35 to 1.90 per bivalent. Chromosomes in Cienfuegosia fall in about the same size range as those of three species of Gossypium L. drawn for comparative purposes (representatives of the A, C, and D genomes, with large, intermediate, and small chromosomes, respectively). Some plants of one species, Cienfuegosia rosei Fryx., show attenuated bivalents, conspicuous cytological irregularities, and pollen sterility. Analysis of F1 intrasectional hybrids involving six species of Cienfuegosia shows that (a) chromosome pairing is similar to that of the parents; (b) sporad irregularities are no greater than in the parents; (c) chiasma frequencies are significantly lower than in the parents; (d) pollen stainability varies from 0 to 93%. F2 plants raised from three interspecific combinations also show normal pairing, vary considerably in chiasma and univalent frequencies, in sporad regularity, and in pollen stainability. The four species of Hampea have a chromosome number of n = 13, which fact supports morphological evidence that this genus is allied with Gossypium and Thespesia Sol. ex Corr The morphologically natural group, tribe Gossypieae, which includes Cienfuegosia, Gossypium, and Hampea, has an aneuploid series of basic chromosome numbers varying from n = 10 to n = 13 (n = 26 in a few tetraploid species of Gossypium). While it is possible that these basic numbers may have been established anciently by allopolyploidy, radiation of the modern species and subspecific taxa has proceeded mainly at the 10-13 chromosome level. This situation is contrasted with that in members of the tribes Ureneae, Malveae, and Hibisceae, where several levels of ploidy may occur in one natural alliance.
Bulletin of the Torrey Botanical Club © 1970 Torrey Botanical Society