Comparative cytogenetics study via fluorescent chromosome banding of three Solanum L. species

Solanum L. subg. Solanum sect. Solanum has a wide distribution in Egypt with multiple overlapping morphological features, rendering the taxonomy of the Solanum nigrum complex difficult at the species level. This study focused on the S. nigrum complex, which consists of S. nigrum L., S. sinaicum Boiss., and S. villosum Mill. Cytogenetic characterization can provide additional taxonomic data and can be used to evaluate genetic diversity at the species level. We performed karyotype analysis of 3 Egyptian species for the first time by studying fluorescence banding patterns via 4’6-diamidino-2-phenylindole (DAPI) and chromomycin A3 (CMA). The three species vary noticeably in their karyotype formulas and genome sizes. Polyploidy has previously been recorded in S. nigrum and S. villosum, and confirmed in this study. In addition, the studied species differ greatly in the number and position of C-bands, CMA bands, and DAPI bands. The distribution of the CMA and DAPI bands reflects the heterochromatin composition and variations acquired by different species. This characterization can be used to assess phylogenetic relationships in the understudied Solanum complex and may serve as a basis for other genomic analyses and evolutionary studies.