Polyploidy: Evolution and crop improvement

The condition of possessing more than two complete genomes in a cell has intrigued biologists almost a century. Many plant species including flowering plants are polyploids, and we know that it has a significant role in the evolution and crop improvement. It is well tolerated in many groups of eukaryotes. Polyploid ancestors have given rise to a number of flowering plants. Despite its widespread occurrence, the direct effect of polyploidy on evolutionary success of a species is still largely unknown. Many attractive hypotheses have been proposed in order to assign functionality to the increased content of a duplicated genome. Among these hypotheses are the proposals that genome doubling confers various advantages to polyploids which allow them to thrive well in environments that pose challenges to their diploid progenitors. Polyploidy is often accompanied with formation of improved varieties, developing sterile lines, restoring fertility in hybrids, enlargement and enhanced vigor, increasing allelic diversity and heterozygosity, etc. In genome-wide context for optimizing marker-assisted selection and crop plant improvement, all these factors need to be considered. This chapter attempts to give a brief overview of polyploidy, its origin, and role in evolution and crop improvement.