Abstract:
Rice (Oryza sativa L.) has been involved in the cultures and agriculture of East and Southeast Asian peoples for a long time. Ethnolinguistic diversity and human migration have played key roles in shaping the remarkable genetic variation of rice in these regions. Mon-Khmer-speaking peoples are thought to be the first to introduced rice cultivation from southern China to northern Thailand during the Neolithic period, but the genetic and morphological characteristics of their traditional landraces remain underexplored. In this study, 100 Mon-Khmer indigenous rice samples, collected from 11 villages of Khmuic and Palaungic language branches, were analyzed using genome-wide SNP markers, together with morphological observations and geographical location. The genetic structure showed strong correspondence with ethnolinguistic identity, Khmuic rice populations were highly uniform and aligned with Subtropical Japonica ancestry, likely reflecting localized seed exchange in their community. In contrast, Palaungic rice displayed greater genetic diversity and admixture, including both Japonica and Indica backgrounds, consistent with more dynamic seed exchange and intercommunity interaction. Morphological differences paralleled genetic structure, with Khmuic rice typically darker in pericarp color and Palaungic rice exhibiting a lighter range. These phenotypic patterns were shaped by both environmental adaptation and the cultural preferences for rice consumption of each ethnic group. In investigating the correlation between genetics, ethnicity, and planting locations, it was found that genetic variation in Japonica rice was primarily associated with ethnolinguistic identity, while elevation played a stronger role in structuring Indica genetic patterns. Overall, these findings show that traditional rice diversity in Mon-Khmer-speaking groups is a result of different evolutionary forces across subspecies, in combination with community development, geography, and culture. All indigenous rice varieties are valuable to conserve as new genetic resources for future rice breeding and improvement