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.

摘要 尽管决明属（Senna）多数物种的二倍体染色体数为2n=28，但常可观测到染色体数目变异，此类变异由多倍化（polyploidy，2n=42、56、112）或异倍化（disploidy，2n=22、24、26）事件引发。为深入解析决明属的核型变异特征，本研究采用色霉素A3（chromomycin A3, CMA）与4',6-二脒基-2-苯基吲哚（4’6-diamidino-2-phenylindole, DAPI）染色技术，对该属10个物种的异染色质分布模式进行了检测，并系统梳理了该属72个物种的染色体计数相关资料。结果显示，10个供试物种的CMA/DAPI带型存在显著差异，具体体现在带纹数量（2至26条不等）及其在染色体上的位置（末端区域或近着丝粒区域）两个方面。本研究的综述分析表明，尽管存在其他染色体数目类型，但2n=28仍是决明属物种中最常见的倍性水平；此外研究中还观测到了多体性（polysomy）与非整倍性（aneusomy）现象。核型变异可能推动了决明属物种的多样化进程与广泛分布。