Polyploidy – whole-genome duplication (WGD) – is a fundamental driver of biodiversity with significant consequences for genome structure, organization, and evolution. Once considered a speciation process common only in plants, polyploidy is now recognized to have played a major role in the structure, gene content, and evolution of most eukaryotic genomes. In fact, the diversity of eukaryotes seems closely tied to multiple WGDs. Polyploidy generates new genomic interactions – initially resulting in “genomic and transcriptomic shock” – that must be resolved in a new polyploid lineage. This process essentially acts as a “reset” button, resulting in genomic changes that may ultimately promote adaptive speciation. This book brings together for the first time the conceptual and theoretical underpinnings of polyploid genome evolution with syntheses of the patterns and processes of genome evolution in diverse polyploid groups. Because polyploidy is most common and best studied in plants, the book emphasizes plant models, but recent studies of vertebrates and fungi are providing fresh perspectives on factors that allow polyploid speciation and shape polyploid genomes. The emerging paradigm is that polyploidy – through alterations in genome structure and gene regulation – generates genetic and phenotypic novelty that manifests itself at the chromosomal, physiological, and organismal levels, with long-term ecological and evolutionary consequences.

Polyploidy plays an important role in biological diversity, trait improvement, and plant species survival. Understanding the evolutionary phenomenon of polyploidy is a key challenge for plant and crop scientists. This book is made up of contributions from leading researchers in the field from around the world, providing a truly global review of the subject. Providing broad-ranging coverage, and up-to-date information from some of the world’s leading researchers, this book is an invaluable resource for geneticists, plant and crop scientists, and evolutionary biologists.

Polyploidy as a dramatic mutational event in the process of evolution has wide implications in nature and for the generation of new and improved crops. The three day Conference on POLYPLOIDY: BIOLOGICAL RELEVANCE focused on three aspects of this natural phenomenon: the first emphasized the characteristics of polyploidy, the second described the occurrence of polyploidy among plants and animals, and the third considered past and future areas of both fundamental and pragmatic research that involve polyploidy. New information relative to origin, cytogenetics, ecology, physiology, biochemistry, and populational studies stress the need to reexamine current views on the origins of polyploidy and its significance among both plants and animals. There are major differences in the occurrence of polyploidy between. plant groups and it is proving a much more common event among bisexual vertebrates than heretofore considered possible. Crop development and improvement must utilize approaches based fundamentally on more natural systems; in fact future research should focus more on polyploidy as a natural phenomenon that needs study at all levels of endeavor from field-oriented populational aspects to sophisticated molecular analyses and genome manipulations. This volume provides a summary of current knowledge of polyploidy pertinent to botanists, zoologists, and agriculturists who are interested in the evolution o~natural systems and who are concerned with the contribution that crop improvement can make to human well-being. Walter H. Lewis St. Louis, Missouri October, 1979 v ACKNOWLEDGMENTS The Host Committee thanks all speakers and moderators for their generous contribution to the Conference and to this volume.

Recent major advances in the field of comparative genomics and cytogenomics of plants, particularly associated with the completion of ambitious genome projects, have uncovered astonishing facets of the architecture and evolutionary history of plant genomes. The aim of this book was to review these recent developments as well as their implications in our understanding of the mechanisms which drive plant diversity. New insights into the evolution of gene functions, gene families and genome size are presented, with particular emphasis on the evolutionary impact of polyploidization and transposable elements. Knowledge on the structure and evolution of plant sex chromosomes, centromeres and microRNAs is reviewed and updated. Taken together, the contributions by internationally recognized experts present a panoramic overview of the structural features and evolutionary dynamics of plant genomes.This volume of Genome Dynamics will provide researchers, teachers and students in the fields of biology and agronomy with a valuable source of current knowledge on plant genomes.

Maize is one of the world’s highest value crops, with a multibillion dollar annual contribution to agriculture. The great adaptability and high yields available for maize as a food, feed and forage crop have led to its current production on over 140 million hectares worldwide, with acreage continuing to grow at the expense of other crops. In terms of tons of cereal grain produced worldwide, maize has been number one for many years. Moreover, maize is expanding its contribution to non-food uses, including as a major source of ethanol as a fuel additive or fuel alternative in the US. In addition, maize has been at the center of the transgenic plant controversy, serving as the first food crop with released transgenic varieties. By 2008, maize will have its genome sequence released, providing the sequence of the first average-size plant genome (the four plant genomes that are now sequenced come from unusually tiny genomes) and of the most complex genome sequenced from any organism. Among plant science researchers, maize has the second largest and most productive research community, trailing only the Arabidopsis community in scale and significance. At the applied research and commercial improvement levels, maize has no peers in agriculture, and consists of thousands of contributors worthwhile. A comprehensive book on the biology of maize has not been published. The "Handbook of Maize: the Genetics and Genomics" center on the past, present and future of maize as a model for plant science research and crop improvement. The books include brief, focused chapters from the foremost maize experts and feature a succinct collection of informative images representing the maize germplasm collection.

Polyploidy and hybridisation are critical processes in plant evolution and speciation. Many current agricultural crops are either natural or agricultural hybrids or polyploids, including potato, sugarcane, wheat, strawberries, and banana. There is a great deal of potential to utilise these natural evolutionary processes for targeted crop improve