Giemsa C-banding Karyotype and Detection of Polymorphic Constitutive Heterochromatin in Nigella sativa L.

Abstract

Karyomorphology, distribution of constitutive heterochromatin, and intrapopulation polymorphism of C-bands in a cross-pollinated population of Nigella sativa L. were studied. Enzymatic digestion of the cell wall allows cytoplasm-free chromosome preparation and enhances the stain resolution, thereby promoting accurate chromosome measurements and identification of chromosomal landmarks. The diploid chromosome number is 2n=12, of which five pairs are moderately long and have median centromere, whereas one small pair has a subterminal centromere. Secondary constriction has been observed in two pairs of long chromosomes. Polymorphism of the C-band size in individuals of the same population and even between two homologous chromosomes of a single individual has been detected by the C-banding technique. Further, the absence of any DAPI-bands indicated that the DNA of C-band region is not AT-rich. The heterogeneity of C-bands in homologous pairs of a single individual is a consequence of cross-pollination where chromosomes come from two different parents. The pattern of heterochromatin distribution can serve as a unique marker that can enrich the karyosystematic database and prove useful in the breeding program of N. sativa.