Genetic diversity patterns of rice (Oryza sativa L.) landraces after migration by Tai Lue and Akha between China and Thailand

Cultivated rice (Oryza sativa L.) is genetically diverse, and the numerous landraces represent a valuable genetic resource for present and future rice breeding. Part of the genetic rice diversity is held by the ethnic minority groups of Tai Lue and Akha who migrated from southern China to northern Thailand over the past two centuries. We analysed variation in simple sequence repeats (SSR) and an indel in the ORF100 region in their rice germplasms in Thailand and in China to understand if the communities today in the Nan and Chang Rai provinces in Thailand still cultivate traditional rice landraces of the Xishungbanna region in southern China, and how such traditional germplasms have evolved in isolation after the human migrations. We found one multilocus genotype shared by all upland rice populations in China and Thailand and that several allelic combinations of the Thai populations can be traced to the alleles pools of upland and paddy rice of the Xishungbanna rice populations. However the frequent occurrence of hybrids between upland and paddy rice in the Thai and Chinese germplasms of both the ethnic communities reveal genetic erosion of the traditional landraces due to hybridization and introgression.