The cultivated Brassica species include numerous vegetable and oil crops of global importance. Three genomes (designated A, B and C) share mesohexapolyploid ancestry and occur both singly and in each pairwise combination to define the Brassica species. With organizational errors (such as misplaced genome segments) corrected, we showed that the fundamental structure of each of the genomes is the same, irrespective of the species in which it occurs. This enabled us to clarify genome evolutionary pathways, including updating the Ancestral Crucifer Karyotype (ACK) block organization and providing support for the Brassica mesohexaploidy having occurred via a two-step process. We then constructed genus-wide pan-genomes, drawing from genes present in any species in which the respective genome occurs, which enabled us to provide a global gene nomenclature system for the cultivated Brassica species and develop a methodology to cost-effectively elucidate the genomic impacts of alien introgressions. Our advances not only underpin knowledge-based approaches to the more efficient breeding of Brassica crops but also provide an exemplar for the study of other polyploids.

Agriculture and Agri Food Canada Saskatoon Saskatchewan Canada

Department of Biology University of York York UK

Department of Horticulture College of Agriculture and Biotechnology Zhejiang University Hangzhou China

Department of Horticulture Shenyang Agricultural University Shenyang China

Department of Plant Breeding and Genetics Punjab Agricultural University Ludhiana India

Department of Plant Breeding Justus Liebig University of Giessen Giessen Germany

Global Institute for Food Security University of Saskatchewan Saskatoon Saskatchewan Canada

Institute of Vegetables and Flowers Chinese Academy of Agricultural Sciences Beijing China

National Key Laboratory of Crop Genetic Improvement College of Plant Science and Technology Huazhong Agricultural University Wuhan China

School of Biological Sciences and the Institute of Agriculture Faculty of Science The University of Western Australia Crawley Western Australia Australia

Selgen a s Plant breeding station Chlumec nad Cidlinou Czech Republic

Southern Cross Plant Science Southern Cross University Lismore New South Wales Australia

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