A cytogenetic study of Polytrias amaura (Poaceae)

A karyomorphological characterization of Polytrias amaura (Poaceae) was performed using orcein staining, sequential fluorescent staining with chromomycin A3 (CMA) and 4',6-diamidino-2-phenylindole (DAPI), and fluorescence in situ hybridization (FISH) method. The common somatic complement with 20 chromosomes were observed in all metaphase cells analyzed. Mitotic chromosomes in respective chromosome complement showed a gradual decrease in size from the largest to the smallest chromosomes. The largest and the smallest chromosome lengths at metaphase were 3.5 μm and 2.0 μm, respectively. The fluorochromes of CMA and DAPI gave reproducible condensation pattern to every prometaphase chromosome, but not metaphse. Each chromosome displayed a characteristic condensation pattern, which was quite same between differential staining methods of GC-specific CMA and AT-specific DAPI. In FISH, two bright 5S rDNA signals were detected at interstitial region of the chromosomes.