Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 20, 2011
Publication Date: February 15, 2012
Citation: Jauhar, P.P. 2012. Polyploidy in relation to plant speciation and evolution. In: Sharma, A.K., editor. Biological Diversity: Principles and Processes. New Delhi, India: Viva Books Pvt. Limited. p. 13-31. Technical Abstract: Polyploidy is a dominant force in plant evolution and speciation. Allopolyploids, resulting from interspecific or intergeneric hybridization coupled with chromosome doubling, are preponderant in nature. For the meiotic and reproductive stability of the allopolyploids, a precise genetic control of chromosome pairing is essential, and was established during evolution. Many of the crop plants are of allopolyploid origin. Tetraploid durum (Triticum turgidum L., 2n = 4x = 28; AABB genomes) and bread wheat (Triticum aestivum L., 2n = 6x = 42; AABBDD genomes) present excellent examples of evolution through allopolyploidy. They are the stabilized “natural hybrids” of wild diploid species. Thus, the allopolyploids enjoy the benefits of stable polyploidy as well as hybridity. Various steps in the origin of these allopolyploids are discussed here. To gain insight into the mechanism of evolution of durum wheat, the present author produced its haploids (polyhaploids) (2n = 2x = 14; AB genomes) and studied their chromosome behavior during meiosis. The polyhaploids produced unreduced gametes through meiotic restitution and also set seed, thereby reconstituting disomic durum wheat. This was in essence a simulation of evolutionary steps that happened in nature thousands of years ago. The study of chromosomes helps unravel several aspects of polyploidy. Various facets of polyploidy in relation to evolution are reviewed and discussed in this article.