Induced Polyploidy in Amaranthus hypochondriacus L. and Amaranthus dubius Mart. ex Thell

Abstract

As a part of the programme of induction of polyploidy in various species of Amaranthaceae, two species viz. Amaranthus hypochondriacus L., a natural dipoid with haploid chromosome number of n=16 and A. dubius Mart. ex Thell., a natural tetraploid with n=32 were selected for the present study with a view to have compara-tive picture of induced polyploidy at tetraploid and octoploid levels.
Various types of morphological changes were noted in colchicine treated plants. Meiotic analysis revealed varied proportions of hexavalents, quadrivalents, bivalents and univalents in the polyploid cells with other cytological abnormalities such as the uneven separation of the chromosomes and the laggards. These result in the organi-sation of the micronuclei and polysporic condition which may account for high degree of pollen and seed sterility.
Comparatively percentage of induction of polyploidy in A. dubius is found to be less than that of A. hypochondriacus. On the other hand frequency and grade of multivalent association is rather higher in A. dubius than those of A. hypochondriacus. The meiotic irregularities in the induced polyploids of A. dubius are also greater than those of A. hypochondriacus which may account for greater percentage of sterility in this induced octoploid.