Autopolyploids of Helianthus annuus L. var. morden

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Autopolyploid plants of Helianthus annuus var. morden were obtained by treating seedlings (2-5 d old) with 0.4%, 0.5% and 0.6% colchicine for 12 h. The autopolyploids exhibited reduction in the height, girth, leaves and flowers of the plants but increase in the size of stomata, pollen grains and meiocytes. Pollen and seed fertility were reduced. There was increase in seed weight from diploids to C<SUB>1</SUB> and then to C<SUB>2</SUB> generations in tetraploids, but increase in C<SUB>1</SUB> and decrease in C<SUB>2</SUB> generation in octoploids. Low seed setting in C<SUB>1</SUB> generation which, however improved in C<SUB>2</SUB> generation only in tetraploids. C<SUB>2</SUB> generation was absent in hexa-decaploids. The chromosome number in diploids, tetraploids, octoploids and hexa-decaploids were found to be 2n=34, 68, 136 and 272, respectively. Meiotic observations showed various associations of chromosomes such as univalents, bivalents and quadrivalents and abnormalities such as laggards, unequal separation of chromosomes, bridges, stickiness in C<SUB>1</SUB> generation which lessened in C<SUB>2</SUB> generation in tetraploids but increase in octoploids. These irregularties appeared to be the major factors responsible for high pollen sterility in autopolyploids. High or number of bivalents and lower frequency of abnormalities at metaphase in tetraploids in C<SUB>2</SUB> generation led to an improvement in pollen and plant fertility.



    CYTOLOGIA 67(2), 213-220, 2002-06-25

    Japan Mendel Society, International Society of Cytology

References:  21


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