Karyotypes and fluorescent chromosome banding patterns in southern African Lycium (Solanaceae)

Chromosomal analyses of several southern African Lycium species resulted in diploid (2n=24: L. amoenum, L. bosciifolium, L. ferocissimum, L. oxycarpum, L. tenue), tetraploid (2n=48: L. gariepense, L. strand-veldense,L. hantamense), and hexaploid (2n=72: L. tetrandrum) counts. Chromosomes in all species were short (mean length = 2.00 mu m; mean haploid genome length = 23.77 mu m). Further, all species shared a highly symmetrical karyotype formula with 10 m pairs and 2 sm pairs, except L. bosciifolium with only one sm pair. The first m pair had a terminal microsatellite on the short arms. Fluorescent chromosome banding patterns with CMA/DAPI staining in the diploid species showed NOR-associated heterochromatin in the first satellited pair. The tetraploids L. gariepense and L. hantamense had two chromosome pairs with a CMA(+)/DAPI(-) terminal band. Phylogenetic studies have shown that the southern African species are included in a monophyletic group including all Old World Lycium; these species are likely of recent origin and, despite ploidy differences, karyotypes are remarkably similar among species. Available data for South American, Asian, and southern African Lycium indicate that there is a common pattern of mostly m chromosomes in which a few cryptic chromosomal rearrangements may have occurred, suggesting that karyotypic orthoselection has preserved similar patterns among species. Thus, these data imply that speciation in Lycium was not accompanied by changes in chromosomal morphology.