Chromosome reports in South American Nicotianeae (Solanaceae) with particular reference to Nierembergia

ACOSTA, M. C.; ORDOÑEZ, A. DEL V.; COCUCCI, A. A.; MOSCONE, E. A.

ANNALS OF THE MISSOURI BOTANICAL GARDEN

Missouri Botanical Garden Press

Año: 2006 vol. 93 p. 634 - 646

0026-6493

Chromosome counts and karyotype information from 41 populations of 20 species and 6 varieties of Nicotianeae (Solanaceae) from South America belonging to Bouchetia (x = 8), Fabiana (x = 9), Leptoglossis (x = 10), Nierembergia (x = 8, 9), and Petunia (x = 7, 9) are given, including first reports from 14 taxa: F. densa, N. ericoides, and  P. patagonica, with 2n = 2x = 18, and N. browallioides, N. calycina, N. graveolens, N. linariifolia var. glabriuscula, var. pampeana, and var. pinifolioides, N. pulchella var. pulchella and var. macrocalyx, N. rivularis, N. tucumanensis, and N. veitchii, with 2n = 2x = 16. All species studied are diploids, with 2n = 16 being the most frequent report. In addition, infraspecific polyploidy is recorded for the first time in N. rigida (2n = 4x = 32) and confirmed in N. aristata (n = 3x = 24, 2n = 6x = 48). In general, karyotypes of the examined species are symmetrical and composed of comparatively small and uniformly sized chromosomes, mostly of the metacentric (m) type except in L. linifolia, P. axillaris, and P. patagonica, where submetacentric (sm) chromosomes are predominant. There are one or rarely two chromosomes bearing nucleolar organizing regions per basic complement. In Nierembergia, karyotype data reflect species grouping. Results suggest that Bouchetia is the closest taxon to Nierembergia, while Leptoglossis, Petunia and Fabiana appear more distant. Possible chromosome number evolution in the tribe is speculated on the bases of molecular phylogenetic studies by other authors. In Nierembergia, x = 9 is proposed as derived from x = 8. Dysploid changes in chromosome number and conservation of chromosome morphology in the karyotypes appear as important evolutionary events in the tribe, whilst polyploidy is noteworthy only in Nicotiana.