The Structure, Stability and Meiotic Behaviour of B-Chromosome in Guizotia Scabra (VIS.) Chiov. SSP. Scabra (Compositae)

SUMMARYA single B-chromosome was found (2n = 2x = 30 + IB) in a few Ethiopian populations of G. scabra ssp. scabra out of several natural populations covering the major distribution range. The B chromosome is small and one third the length of smallest A-chromosome and appears to be heterochromatic. In mitotic and meiotic system it shows numerical stability. The B-chromosome do not pair with any member of A-chromosome complement during meiotic prophase and remains as univalent. The fate of univalent B is variable. In majority of PMCs the single B moves to one of the telophasic nucleus in undivided condition. In subsequent II meiotic division B-chromosome divides normally, with the result out of 4 tetrad nuclei two of them contain 1B each, and others contain no B-chromosomes.