Mitotic and meiotic behaviour of B-chromosomes ofGuizotia scabra(Vis.) Chiov. ssp.scabra(Compositae)

Abstract

SUMMARYGuizotia scabra ssp. scabra plants grown from seeds originating from southwest Ethiopia were found to carry 1–4 and 1–6 B-chromosomes in root tip cells and pollen mother cells, respectively. The B-chromosomes were of three morphological types, being large in size with a median or submedian centromere or smaller in size with a likely median centromere. They are all numerically stable within and between root tips, but in most of the plants their numbers in the pollen mother cells were higher than in the roots. When single, a B-chromosome remained as a univalent. When two or more were present, they paired with one another, most frequently as bivalents, with chiasmata in one or both arms. They had a high frequency of normal segregation at anaphase I and subsequent stages of meiosis. After application of C-banding technique, the large B-chromosomes with a median centromere did not show C-bands.