Intra- and interspecific karyotypic variations of the genus Senna Mill. (Fabaceae, Caesalpinioideae)

Abstract

Although the chromosome number 2n = 28 predominates in most species of the genus Senna, variations are often observed, resulting from either polyploidy (2n = 42, 56, 112) or disploidy (2n = 22, 24, 26) events. To better understand the karyotypic variations in Senna, we examined heterochromatin patterns of 10 species of that genus using chromomycin A3 (CMA) and 4'6-diamidino-2-phenylindole (DAPI) staining, and reviewed information on the chromosome counts of 72 species of that genus. The CMA/DAPI banding patterns were relatively variable among the 10 species, both in terms of the numbers of bands (from two to 26) and their locations on the chromosomes (terminal or proximal regions). Our review indicated that 2n = 28 is the most common ploidy among species of Senna, although other numbers were observed, apparently due to polyploidy or disploidy events; polysomy and aneusomy were also observed. Karyotype variations appear to have contributed to the diversification and wide distribution of Senna.