Polyploidy and Crop Improvement

All crop plants are polyploid and some genomes have been duplicated more recently than others. Advancements in cytogenetic and molecular tools, including high‐density genetic mapping, florescent in situ hybridization, and genome and EST sequencing, have enabled new insights into genome composition and the history of genome duplications in crop plants. We review this evidence and discuss the relevance of genome duplication to crop improvement. Polyploidy provides genome buffering, increased allelic diversity and heterozygosity, and permits novel phenotypic variation to be generated. Polyploid formation is often accompanied with loss of duplicated chromatin, changes in gene expression, novel epistatic interactions, and endosperm effects. All of these factors need be considered in a genome‐wide context for optimizing marker assisted selection and crop plant improvement.