Karyotype diversity and genome size in the Cyphomandra clade of Solanum L. (Solanaceae)

Abstract The Cyphomandra clade, a distinct group within the Solanum L. genus, is characterized by remarkable traits, including large chromosomes and big genome sizes. We aimed to investigate whether these features are conserved within the Cyphomandra clade and how they differentiate this group from other Solanum species. We elaborated karyotypes based on CMA/DAPI banding and rDNA fluorescence in situ hybridization (FISH) and estimated the genome size from 12 species, eight belonging to Cyphomandra and four from related clades. All species showed metacentric or submetacentric chromosomes and symmetrical karyotypes, with 2n = 24, except S. mammosum L. (2n = 22). CMA/DAPI banding in combination with rDNA FISH revealed three distinct patterns of heterochromatin distribution (number and position of bands, all CMA+). Most species showed one pair of 35S and 5S rDNA on different chromosomes, except S. mammosum (one of the two pairs was observed in the same chromosome). Notable, the Cyphomandra clade species showed larger chromosomes and genome sizes than other species of Solanum, corroborating that these karyotype attributes are valuable to characterize the clade. The number of CMA/DAPI bands and rDNA sites does not justify the differences in the genome size. Therefore, the accumulation and dispersion of other repetitive sequences, like transposable elements, may be associated with the karyotype changes.