Karyotype analysis of Lablab purpureus (L.) Sweet using fluorochrome banding and fluorescence in situ hybridisation with rDNA probes

Abstract

The mitotic chromosomes of Lablab purpureus (L.) Sweet were characterised using sequential combined propidium iodide (PI) and 4',6-diamidino-2-phenylindole (DAPI) (CPD) staining and fluorescence in situ hybridisation (FISH) with 5S and 45S rDNA probes. The detailed karyotype of this species was established using prometaphase chromosomes. After CPD staining, CPD and DAPI+ bands were shown simultaneously. CPD bands occurred in the proximal regions of the long arms of all chromosome pairs and at all 45S rDNA sites, while the DAPI+ bands appeared in all centromeres. FISH with rDNA probes revealed one 5S locus and eight 45S loci. The single 5S locus was interstitially located on the long arms of the shortest chromosome pair. Among the 45S loci, two large loci were located in the secondary constrictions of the short arms of two chromosome pairs; six small or minimal loci were proximally located on the short or long arms of six chromosome pairs. Each prometaphase chromosome pair could be identified using the CPD and DAPI+ bands, the rDNA-FISH signals in combination with the chromosome measurements and condensation patterns. The karyotype was formulated as 2n = 2x = 22 = 14m (2SAT) + 6sm + 2st (2SAT), and the asymmetry indices, CI, A1, A2, As K%, AI and the Stebbins category were 38.23 ± 7.06, 0.36, 0.31, 61.99, 5.68 and 2B, respectively.

Keywords

• combined pi and dapi staining
• fish
• hyacinth bean
• karyotyping
• ribosomal gene