Domestication history and geographical adaptation inferred from a SNP map of African rice

Rachel Meyer and colleagues use whole-genome resequencing of 93 African rice landraces to generate a SNP map used for population analysis and a genome-wide association study for salt tolerance traits. They find 11 significant loci, some with signatures of positive selection, and evidence for a population bottleneck beginning around 15,000 years ago. African rice (Oryza glaberrima Steud.) is a cereal crop species closely related to Asian rice (Oryza sativa L.) but was independently domesticated in West Africa ∼3,000 years ago1,2,3. African rice is rarely grown outside sub-Saharan Africa but is of global interest because of its tolerance to abiotic stresses4,5. Here we describe a map of 2.32 million SNPs of African rice from whole-genome resequencing of 93 landraces. Population genomic analysis shows a population bottleneck in this species that began ∼13,000–15,000 years ago with effective population size reaching its minimum value ∼3,500 years ago, suggesting a protracted period of population size reduction likely commencing with predomestication management and/or cultivation. Genome-wide association studies (GWAS) for six salt tolerance traits identify 11 significant loci, 4 of which are within ∼300 kb of genomic regions that possess signatures of positive selection, suggesting adaptive geographical divergence for salt tolerance in this species.