Comparative Fluorescent Banding in Two Forms of Leonurus sibiricus L.

Abstract

The karyotypes of wild Leonurus sibiricus L. (red flower form) and its extremely rare white flower form were compared after staining with orcein, CMA and DAPI. Both the forms were found to possess 2n=20 chromosomes. These 2 forms have similar centromeric formulae of 16m+4sm indicating less variation in their karyotypes and thus could be considered as symmetric karyotypes. Four CMA-positive bands were found in the white flower form and 7 in the red flower form. The distribution, location and intensity of these bands were quite different. Moreover, the percentage of the GC-rich region is almost double in the red flower form. The white flower form possessed no DAPI-positive bands whereas a pair of terminal DAPI bands was found in the other form. It was possible to identify some marker chromosomes with CMA and DAPI staining which are specific to each karyotype. Fluorescent banding indicated the occurrence of minute deletion and paracentric inversion in the genomes of these 2 forms. The present results revealed that these 2 forms were not similar in respect of fluorescent karyotypes and, therefore, a peer revision regarding their taxonomic position is necessary.