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Nature and Behaviour of B Chromosomes in Allium Stracheyii Baker and Urginea Indica Kunth
Published in -
Volume: 39
Issue: 2
Pages: 245 - 251
The nature and behaviour of B chromosomes in Allium stracheyii and Urginea indica have been studied in detail. In A. stracheyii, a correlated analysis of their behaviour in root cells, pollen mother cells and pollen grains has been carried out. The presence of defective but functioning centromere has been suggested. The heterochromatic constitution of the Bs has been demonstrated. It has been shown that there is no selection barrier for the Bs to enter into the germinal line, though in the pollen grains, over and below a threshold, the B chromosomes are not favoured. The selective value of B chromosomes is exhibited by their presence in every individual of the population. As in A. stracheyii, in the U. indica as well, tetraploids are devoid of B chromosomes indicating that the adaptability conferred by Bs is not needed in tetraploids with increased tolerance range. The origin of B chromosomes has been suggested through elimination of euchromatic segments from triploids or aneuploids. © 1974, Japan Mendel Society, International Society of Cytology. All rights reserved.
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