engleski

Distribution of heterochromatin and location of nucleolar organizing region in Allium commutatum Guss.

Background and purpose. Regarding to the fact that most of the Mediterranean species in subg. Allium, sect. Allium, which Allium commutatum belongs, have very similar karyomorphological characteristics, it is very difficult to obtain taxonomic and phylogenetic relationships by convenient karyotype analysis. The aim of this study was to establish the karyotype of A. commutatum according to the distribution and characteristics of heterochromatin. Materials and methods. Plants from Palagruža island were used for karyomorphological analysis. For standard karyotype analysis as well as meiotic events in pollen mother cells, chromosomes were stained with 2% acetokarmine, while for heterochromatic banding pattern two Giemsa C-banding techniques were used. For determination of NOR position staining with chromomycin A3 (CMA) and DAPI were used, while silver staining was applied for NOR activity analysis. Results and conclusions. Investigated plants of A. commutatum have diploid chromosome complement 2n=2x=16 metacentric, submetacentric and subtelocentric chromosomes with secondary constrictions located proximal to the centromere of one submetacentric pair and median in short arm of subtelocentric pair. Giemsa C-banding technique revealed centromeric, telomeric, intercalary and secondary constriction C-bands. Staining with CMA revealed CMA-positive bands in secondary constrictions of both VII and VIII chromosome pairs that correspond with DAPI-negative bands. Silver staining confirmed that secondary constrictions represent a position of active nucleolar organizing regions (NORs). On the base of our investigations three chromosomes (VI, VII and VIII) could be distinguished as marker chromosomes that could help in determination of relationships in inter- and intraspecific level.

Allium commutatum Guss.; karyotype; Giemsa C-banding; fluorochrome banding; silver staining; nucleolar organizing region

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