Revisiting the dispersal history of walnut by analyzing the ancient DNA of walnut remains in Xinjiang, China

Persian walnut is an important crop with a disputed history of domestication origins and dispersal. Xinjiang, a key hub in East-West exchanges, was selected for sample analysis from three time points. This study presents genome-wide data from ancient walnut remains dating to the Tang Dynasty. Phylogenetic analysis of Eurasian walnut accessions and iron walnut endemic to southwest China indicates that ancient Xinjiang walnut represents a genetic transitional stage between South Central Asian and eastern Chinese accessions. The relatively recent ancient remains show the greatest similarity to modern Xinjiang cultivars. Consistent with previous research, walnut populations from Central Asia and its surrounding regions exhibit the highest diversity, supporting their role as the center of origin and domestication, while European and East Asian populations display lower diversity. These findings highlight Xinjiang's critical role as a corridor for the spread of walnut across China and the value of ancient DNA for reconstructing crop history.