Genomics Study On The Ancient Remains Of Setaria Italica And Panicum Miliaceum From Xinjiang

Setaria italica（L.）Beauv.and Panicum miliaceum L.have a long history of cultivation in China.According to archaeological research,S.italica and P.miliaceum were domesticated in northern China about 10,000 years ago and then spread to Eurasia and other places.Xinjiang is an important transportation hub for cultural exchange and human migration between the East and the West,it is located in the hinterland of Eurasia,connecting the East and the west of Eurasia,and undertaking the material and technological circulation and population exchange between each other,it is also considered to be a channel for the westward expansion of S.italica and P.miliaceum dry farming.In this study,we selected ancient remains of S.italica and P.miliaceum of from Xinjiang,and successfully obtained ancient DNA from three ancient remains（two grains remains and one leaf remains）S.italica from Wupu cemetery（3000～2400 years ago）,and from three ancient remains of（grains remains）P.miliaceum from Xiaohe cemetery（about 3650 ～ 3450 years ago）,Subeixi cemetery（about2400～2300 years ago）and Asitana cemetery（about 1300～1200 years ago）as well.The genome data of ancient remains of S.italica and P.miliaceum were compared with the genome data of modern populations of S.italica and P.miliaceum,and genetic analysis of S.italica and P.miliaceum.The results of plant ancient DNA extraction show that the preservation of ancient DNA in plant remains is closely related not only to the type of sample materials and preservation time,but also to the preservation environment of the sites.The population genetic analysis of ancient and modern S.italica samples shows that the S.italica in North China and the Loess Plateau has high genetic diversity,indicating that these areas may be the domestication sites and genetic diversity center of S.italica,the genetic relationship between ancient S.italica samples and modern S.italica samples in northern China,including Gansu,is relatively close,indicating that after domestication in northern China,Chinese S.italica was introduced into Xinjiang through Gansu Hexi corridor to the west,and then to the western part of Eurasia.Hexi Corridor is the key node of S.italica to Xinjiang;the genetic structure of ancient S.italica remains in Wupu cemetery is similar to that of modern S.italica in Xinjiang,indicating that there may not have changed significantly in the genetic structure of S.italica in Xinjiang in recent 3000 years.The population genetic analysis of ancient and modern P.miliaceum samples shows that the ancient P.miliaceum remains sample in Xiaohe cemetery belongs to the type of central and western Eurasia,this type may be formed by genetic differentiation under the influence of planting methods,climate,geographical environment and eating habits in the transmission process of the inner Asian mountain corridor,it is transmitted into Xinjiang after its formation at the inner Asian mountain corridor;the ancient P.miliaceum remains sample in Subeixi cemetery belongs to a mixed type of central and western Eurasia and eastern Eurasia,this type may be formed by the hybridization of two types of central and western Eurasia and eastern Eurasia cultivated millet in the northern Eurasian steppe with the migration of people from eastern Eurasia and western Eurasia,and then introduced to Xinjiang.The ancient P.miliaceum remains sample in ASTN cemetery belongs to the mixed type of central and western Eurasia and wild forms,this type of P.miliaceum has a recent genetic relationship with individuals form Gansu and Xinjiang,it is speculated that this type of millet may be brought into Xinjiang along with the migration of people in northern China from Hexi Corridor of Gansu to Xinjiang.By comparing the genetic structure of S.italica and P.miliaceum populations,we found that P.miliaceum in eastern and central and western Eurasia had obvious genetic divergence,but there was no obvious genetic divergence was found in S.italica populations.We speculate that S.italica and P.miliaceum was domesticated in northern China 10000 years ago and spread westward to western Eurasia,in the process of westward transmission,P.miliaceum may be widely spread in the inner Asian mountain corridor earlier than S.italica due to its stronger resistance and shorter growth period,this transmission process was accompanied by genetic divergence.By comparison,the adaptability of S.italica is weaker than P.miliaceum,so it failed to spread and genetic diivergence at the inner Asian mountain corridor in early stage,which is consistent with the results of archaeological study that S.italica spread later than P.miliaceum in the inner Asian mountain corridor.The present study provides key paleogenomic data for the study on domestication and transmission of S.italica and P.miliaceum,and enriches the evidence of population genetic research of S.italica and P.miliaceum in Xinjiang.At the same time,the genetic diversity and population genetic structure of ancient and modern S.italica,ancient and modern P.miliaceum populations were compared and analyzed,and discussion on the spread route,spread history and spread mechanism of S.italica and P.miliaceum were then made gradually and deeply.The results may lay a theoretical foundation for future related research.