Karyotype, RAPD and ISSR Analysis of Four Specimens in Gynura nepalensis DC

Four specimens of Gynura nepalensis DC. were investigated for authentic characterization by differential cytogenetical and PCR based molecular analysis. Three specimens out of four were collected from different localities of Bangladesh viz. i) from Netrokona district (specimen A), ii) from Dhaka district (specimen B) and iii) from Bogra district (specimen D). On the other hand, specimen C was collected from Canada. The diploid chromosome number of four specimens were 2n=20 with different centromeric formulae such as 14m+6sm in specimens A, B and D while 20m in specimen C. Total length of 2n chromosome complement was 211.61 µm in specimen A, 217.58 µm in specimen B, 168.82 µm in specimen C and 197.80 µm in specimen D. The maximum range of chromosome length was found in specimen B (6.67–14.30 µm) and minimum in specimen C (6.44–10.12 µm). The four specimens have distinct CMA- and DAPI-banding pattern which confined to the terminal regions of respective chromosomes. Karyotype analysis revealed that the number, location and distributions of GC- and AT-rich repeats are different in these four specimens. Heteromorphicity in respect of occurrence of CMA- and DAPI-banding pattern in the homologue members were observed in specimen A, C and D. The heteromorphicity might be a result of deletion of banded region from the respective homologue members. One interstitial CMA band was found on the short arm in a member of pair V in specimen A and in pair IV of specimen C. Two terminal DAPI bands were found in two chromosomes of specimens A and B. These CMA- and DAPI-banded chromosomes were unique and thus could be used as marker chromosomes for the respective specimens. Only specimen C showed RAPD bands with three primers. However, the four specimens had distinguishable ISSR-banding patterns with seven primer combinations. Specimen C showed maximum ISSR bands. The combined RAPD and ISSR analysis placed specimen C in a separate cluster with the highest genetic distance. In spite of very distant location specimens A and D were placed in a sub-cluster with narrow genetic distance.