2016 Volume 81 Issue 3 Pages 349-355
Both male and female Coccinia grandis L. were studied cytogenetically using conventional and fluorochrome dyes. In addition, RAPD was carried out to distinguish the two sexes. In male plants, a pair of prominent satellites was observed, one in each member of pair III. Both male and female plants were found to possess 2n=24 metacentric chromosomes (including “Y-chromosome”). The length of individual chromosomes ranged from 0.97 to 5.03 µm (Y-chromosome) in the male and 0.78 to 1.32 µm in the female plant. The Y-chromosome found in this study was 5.03 µm, which is about 3.06 times bigger than the largest autosome. The interphase nuclei of male specimens possessed a number of thick, round and darkly stained heterochromatic blocks. A bigger and elongated area was also observed in the interphase nuclei of male plants, which indicated the probable appearance of heterochromatic Y-chromosome. A distinct Y-chromosome was observed at prophase after staining with orcein, CMA, and DAPI. The Y-chromosomes were fully fluoresced with both CMA and DAPI, revealing the tandem existence of GC- and AT-rich repeats along the length. The most striking feature is that the Y-chromosome with distinct centromeres was observed even in the interphase nuclei and prophase stages after orcein, CMA, and DAPI staining. It suggested that the Y-chromosomes contracted much earlier than those of autosomes. This feature of the Y-chromosome has not yet been reported and is a new unique feature of Y-chromosomes of C. grandis. Different types of CMA- and DAPI-banding patterns were found in male and female plants, which are characteristic features of each sex. The difference of GC- and AT-rich percentage was due to the Y-chromosome. Four different primers were used for RAPD profiling. Polymorphism of RAPD bands was distinct in male and female plants. Therefore, the compilation of the above information will be very useful for making multidimensional genetic information of male and female C. grandis L. found in Bangladesh.
