Comparative Cytogenetic Study of Eggplant (Solanum melongena L.) and Its Wild Ancestors Solanum insanum L. and Solanum incanum L.

Eggplant (Solanum melongena L., 2n = 2x = 24) is one of the most economically important crop species of the Solanaceae family. In recent decades, various approaches have enabled the identification of Solanum insanum as the direct ancestor and Solanum incanum as the closest wild relative; however, these studies have largely neglected chromosomal features. To expand the chromosome knowledge of eggplant and its ancestors, we performed a comparative cytogenetic study by combining karyomorphological analyses with Fluorescence In Situ Hybridization (FISH) and Genomic In Situ Hybridization (GISH). The three species exhibited similar chromosome morphology, except for the NOR-bearing chromosomes, which distinguished the S. incanum karyotype from those of the other two species. rDNA FISH mapping revealed two distinct patterns: one common to eggplant and S. insanum, and the other exclusive to S. incanum. The s-GISH method, used to examine the chromosome distribution of satDNA repeats, revealed identical patterns, which suggests that the chromosome structure of the investigated species was conserved during their evolution. Hybridization signals from cross-GISH experiments aligned with s-GISH patterns and confirmed the genomic homology among S. melongena, S. insanum and S. incanum. Our study provided novel cytogenetic evidence clarifying the evolutionary relationships between the cultivated eggplant and its ancestors.