C-banding and nucleolar activity of tetraploid Avena species

The Giemsa C-banding pattern of the chromosomes of five tetraploid species of Avena have been studied. The chromosomes of AABB species (A. barbata, A. vaviloviana, and A. abyssinica) had similar C-banding patterns to those of A genome species. AACC species (A. maroccana and A. murphyi) possessed two sets of seven chromosome pairs with C-banding patterns similar to those observed in the diploid A and C genome species. However, no good correspondence between either of these two chromosome groups and any one diploid species has been found. When the nucleolar organizer activity of the species was analysed by silver staining, fewer nucleoli and nucleolar organizer regions (NORs) were observed than expected, assuming complete additivity of those from the donor diploid species.