African rice (Oryza glaberrima) and African cultivation practices are said to have influenced emerging colonial plantation economies in the Americas1,2. However, the level of impact of African rice practices is difficult to establish because of limited written or botanical records2,3. Recent findings of O. glaberrima in rice fields of Suriname Maroons bear evidence of the high level of knowledge about rice among African slaves and their descendants, who consecrate it in ancestor rituals4,5. Here we establish the strong similarity, and hence likely origin, of the first extant New World landrace of O. glaberrima to landraces from the Upper Guinean forests in West Africa. We collected African rice from a Maroon market in Paramaribo, Suriname, propagated it, sequenced its genome6 and compared it with genomes of 109 accessions representing O. glaberrima diversity across West Africa. By analysing 1,649,769 single nucleotide polymorphisms (SNPs) in clustering analyses, the Suriname sample appears sister to an Ivory Coast landrace, and shows no evidence of introgression from Asian rice. Whereas the Dutch took most slaves from Ghana, Benin and Central Africa7, the diaries of slave ship captains record the purchase of food for provisions when sailing along the West African Coast8, offering one possible explanation for the patterns of genetic similarity. This study demonstrates the utility of genomics in understanding the largely unwritten histories of crop cultures of diaspora communities.
We would like to thank rice farmers in Jawjaw, Mundje Kreek, Mooytaki and Paramaribo for sharing their knowledge on African rice with us. T. Polimé and B. Poeketie facilitated fieldwork in Maroon communities. C.-R. Lee helped us with the TPS analysis. This research was funded by the Biosystematics group of Wageningen University, Naturalis Biodiversity Center (Leiden), as well as support from NSF Plant Genome to R.S.M. (IOS-1202803) and M.D.P. (IOS-1126971), a TKI-Horticulture Grant to M.E.S. and S.A.A., grants from the US National Science Foundation and the NYU Abu Dhabi Research Institute to J.M.F., and the AXA Chair in Genome Biology and Evolutionary Genomics to R.A.W.
Background information on the 110 Oryza glaberrima samples used for analysis, including mean depth of sequencing coverage, accession codes, collection locations and clustering distance to Surinamese sample (suri_glab_SUR).
Per cent heterozygosity of African rice accessions with additional country labels.
Filtering of polymorphisms. Multi Nucleotide Polymorphisms (MNP) were always excluded. Heterozygous (HET) SNPs and regions with no coverage (NC) were tentatively excluded as well but their frequency was too high.
Top 10 EIGENSTRAT principal components of the 110 Oryza glaberrima samples.
Ethnolinguistic information on sample provenances. Ethnolinguistic classification of locations from which the samples were collected.
Genetic distance between the O. glaberrima samples. Kruskal-Wallis multiple comparison tests. A Kruskal-Wallis test showed significant differences in genetic distances to the Surinamese sample by country (where country n>1) (Kruskal-Wallis chi-squared = 53.809, df = 11, p-value = 1.279e-07). Results reported are for the multiple comparison test following Kruskal-Wallis set to Bonferroni significance of alpha = 0.05 after correction for 66 tests (P<0.00075).