Chromosome Reports in South American Nicotianeae (Solanaceae), With Particular Reference to Nierembergia1,2

Chromosome counts and karyotype information from 41 populations of 20 species and 6 varieties of Nicotianeae (Solanaceae) from South America belonging to Bouchetia Dunal (x = 8), Fabiana Ruiz & Pav. (x = 9), Leptoglossis Benth. (x = 10), Nierembergia Ruiz & Pav. (x = 8, 9), and Petunia Juss. (x = 7, 9) are given, including first reports from 14 taxa: F. densa Rémy, N. ericoides Miers, and P. patagonica (Speg.) Millán, with 2n = 2x = 18, and N. browallioides Griseb., N. calycina Hook., N. graveolens A. St.-Hil., N. linariifolia Graham var. glabriuscula (Dunal) A. A. Cocucci & Hunz., var. pampeana (Millán) A. A. Cocucci & Hunz., and var. pinifolioides (Millán) A. A. Cocucci & Hunz., N. pulchella Miers var. pulchella and var. macrocalyx (Millán) A. A. Cocucci & Hunz., N. rivularis Miers, N. tucumanensis Millán, and N. veitchii Hook., with 2n = 2x = 16. All species studied are diploids, and most have 2n = 16. In addition, infraspecific polyploidy is recorded for the first time in N. rigida Miers (2n = 4x = 32) and confirmed in N. aristata D. Don (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 (Miers) Griseb., P. axillaris (Lam.) Britton, Stern & Poggenb., 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 based on molecular phylogenetic studies by other authors. In Nierembergia, x = 9 is proposed to be 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, while polyploidy is noteworthy only in Nicotiana L.