Polyploidy In Plants

INTRODUCTION

One of the remarkable features of living material is their ability to perpetuate themselves. However, the ever dynamic nature of the surrounding environment has imposed upon plants, much like other organisms, various evolutionary and selective bottlenecks necessitating the adoption of ways and means by organisms to keep their “race going”. A concept which gains prominence in this regard is that of hybridization and has been an area of much fascination since the eighteenth century. Stebbins defined hybridization as the “crossing between individuals belonging to separate populations which possess different adaptive norms”1. Polyploidy, a prime facilitator of speciation and evolution in plants and to a lesser extent in animals is

As pointed out at the very outset it is recognized as one of the main process in the evolutionary history of plants and to some extent other organisms. Though differences do exist with regard to the nature of its role and the relative importance of different kinds of polyploidy, an understanding of the ways in which polyploidy operated in the past to produce new species and races may provide useful insights to improving our cultivated plants. In fact many of our crop species, including wheat, maize, sugar cane, coffee, cotton and tobacco, are polyploid, either through intentional hybridization and selective breeding (e.g. some blueberry cultivars) or as a result of a more ancient polyploidization event(e.g. maize)5. Added to it, a technological advance in the analysis of genome structure and function has made it possible to better analyze the genetic consequences of genome duplication. The importance of polyploidy in such diverse fields such as cytogenetics, physiology, breeding, cytotaxonomy and biogeography in conjunction with new possibilities put forth by various molecular techniques has all spurred a resurgence of interest in issues of origin and establishment of

With regard to the breeding system since the main mode of origin of allopolyploids in annuals is by the fusion of unreduced gametes, the presence of an outcrossing breeding system tends to reduce the chances of union of unreduced gametes. A perennial growth habit tends to favor polyploidy as opposed to an annual growth habit, probably due to the fact that having a long life span increases the chances that