First karyotypic register of Ctenodon elegans (Leguminosae: Papilionoideae: Dalbergieae) from Puebla, Mexico, using splash method and Giemsa staining

The genus Ctenodon was recently reestablished to include the Ochopodium section of Aeschynomene. This genus is composed of 78 species and infraspecific taxa that are found in the Neotropics. However, quantitative cytogenetic information is only available for three of these species. To describe the chromosome morphology of Ctenodon elegans, a species with a wide distribution in tropical America, an air-drying (splash) method and Giemsa staining were used. Chromosome complements in metaphase and prometaphase showed a diploid chromosome number of 2n=20, which is common in the dalbergioid clade. The karyotype formula obtained, 9m+1sm, is like that of another cogeneric species. However, other cytogenetic parameters differ from those of previously studied species. These results confirm a wide chromosome diversity in Ctenodon, including differences in the arrangement of satellite (SAT) chromosomes considered nucleolar organizer region (NOR) chromosomes within the karyotype. The study also highlights that total and average chromosome size are not the most important parameters in the comparative cytogenetics of the genus. Other parameters, such as karyotype symmetry, must be considered to advance our understanding of chromosome evolution in dalbergioids.