Genome sequencing of adzuki bean (Vigna angularis) provides insight into high starch and low fat accumulation and domestication

Adzuki bean (Vigna angularis), an important legume crop, is grown in more than 30 countries of the world. The seed of adzuki bean, as an important source of starch, digestible protein, mineral elements, and vitamins, is widely used foods for at least a billion people. Here, we generated a high-quality draft genome sequence of adzuki bean by whole-genome shotgun sequencing. The assembled contig sequences reached to 450 Mb (83% of the genome) with an N50 of 38 kb, and the total scaffold sequences were 466.7 Mb with an N50 of 1.29 Mb. Of them, 372.9 Mb of scaffold sequences were assigned to the 11 chromosomes of adzuki bean by using a single nucleotide polymorphism genetic map. A total of 34,183 protein-coding genes were predicted. Functional analysis revealed that significant differences in starch and fat content between adzuki bean and soybean were likely due to transcriptional abundance, rather than copy number variations, of the genes related to starch and oil synthesis. We detected strong selection signals in domestication by the population analysis of 50 accessions including 11 wild, 11 semiwild, 17 landraces, and 11 improved varieties. In addition, the semiwild accessions were illuminated to have a closer relationship to the cultigen accessions than the wild type, suggesting that the semiwild adzuki bean might be a preliminary landrace and play some roles in the adzuki bean domestication. The genome sequence of adzuki bean will facilitate the identification of agronomically important genes and accelerate the improvement of adzuki bean.