The chromosome-scale genome of wild Brassica oleracea provides insights into the domestication of Brassica plants.

The cultivated diploid Brassica oleracea is an important vegetable crop, but the genetic basis of domestication remains largely unclear without high-quality reference genomes of wild B. oleracea. Here, we report the first chromosome-level assembly of the wild Brassica oleracea L. W03 genome, (total genome size, 630.7 Mb; scaffold N50, 64.6 Mb). Using newly assembled W03 genome, we constructed a gene-based B. oleracea pangenome and identified 29,744 core genes, 23,306 dispensable genes, and 1,896 private genes. We resequenced 53 accessions, which represent six potential wild B. oleracea progenitor species. The results of the population genomic analysis showed that wild B. oleracea population had the highest level of diversity and represented the more closely related population of horticultural B. oleracea. Additionally, the WUSCHEL gene was found to play a decisive role in domestication and to be involved in cauliflower and broccoli curd formation. We also illustrate the loss of disease resistance genes during domestication selection. Our results provide deep insights into B. oleracea domestication and will facilitate Brassica crop genetic improvement.