USE OF POLYPLOIDY IN TROPICAL AND SUBTROPICAL PLANT IMPROVEMENT PROGRAMMES

Polyploidy is a condition in which individuals have two or more chromosome sets or genomes in their somatic cells. In contrast to the normal diploid (2n), they may be triploid (3n), tetraploid (4n), pentaploid (5n), hexaploid (6n) etc. Polyploid plants can arise naturally from duplication of chromosomes of a single species (autoploidy) or the combination of two or more chromosome sets of different species (alloploidy). Generally, induced autopolyploids are expected to have at least one of the following characteristics which would result in the improvement, or development of new economically important plants: larger tuber, rhizome or root size; increased fruit size; enhanced flower size and/or colour intensity, improved drought tolerance, increased bio-mass; improved photosynthetic capacity; larger and/or thicker leaves; dwarfism; increased secondary metabolite production e.g. medicinal compounds. The Agricultural Research Council’s Institute for Tropical and Subtropical Crops various Plant Improvement Programmes make use of polyploidy in endeavours towards producing high quality crops with development potential. A review of a few case studies will be presented.