Rice (Oryza sativa) was domesticated in the Yangtze River basin of China and later spread across Asia into Europe, yet the route of its early introduction into Europe remains unresolved because modern breeding and repeated introductions have obscured historical signals in cultivated varieties. Here, we use weedy rice, a feral derivative of cultivated rice that experiences relatively limited artificial selection and retains clearer ancestral genomic features, as a genomic system for tracing historical dispersal. Combing whole-genome resequencing of 196 weedy rice accessions with analyses of photoperiod-related flowering genes, we investigated the evolutionary relationships among Asian and European rice populations. Population genomic and phylogenetic analyses reveal a close genetic affinity between European weedy rice and northwestern Chinese rice lineages, while also identifying signatures of recent feralization and introgression from modern cultivars. Photoperiod-adaptive alleles enriched in northwestern Chinese weedy rice were also prevalent in modern European cultivars, consistent with repeated use of ancestral variation during adaptation to higher latitudes. Demographic modelling suggests that these shared patterns likely predate modern breeding. Together, our results demonstrate the utility of weedy rice for studying crop evolutionary history and provide genetic evidence consistent with a historical westward dispersal of rice into Europe, potentially along routes associated with Silk Road.
Zhong et al. (Sun,) studied this question.