Differentiation Between Hippophae Rhamnoides Subsp. Sinensis And H. Rhamnoides Subsp. Yunnanensis

The genus Hippophae belongs to family Eleagnaceae.At present,there are 7 species and11 subspecies of the genus Hippophae,including 7 species and 7 subspecies are distributed in China.H.rhamnoides subsp.sinenesis and H.rhamnoides subsp.yunnanensis have overlap area geographyly,located in northern and central Sichuan.The classification of this region is controversial.H.rhamnoides subsp.sinensis is widely distributed in Sichuan,Gansu,Qinghai,Shaanxi,Shanxi,Hebei,Inner Mongolia and other provinces.It is widely cultivated in China.Meanwhile,due to the rich morphological differences within H.rhamnoides subsp.sinensis,it is also the appropriate material for studying local adaptation.Researchers put more energy into the study of H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis.In this study,three different molecular markers were used,namely simple repeat sequence(SSR),single nucleotide polymorphism(SNP)and chloroplast DNA(cp DNA),which were used to analyze the genetic structure and differentiation of H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis,as well as to find the potential geographical distribution boundaries between H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis.The main results of this study are as follows:(1)The level of genetic differentiation between H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis was high.Based on SSR and SNP markers,the coefficients of genetic differentiation between the two subspecies were 0.435 and 0.350,respectively.Hongyuan and Songpan counties in northern Sichuan are most likely to be the distribution boundaries of H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis.(2)Based on SSR markers,the genetic diversity of H.rhamnoides subsp.sinensis was higher than that of H.rhamnoides subsp.yunnanensis.The mean coefficients of H.rhamnoides subsp.sinensis,including N_A、N_E、H_O、H_E,were higher than that of H.rhamnoides subsp.yunnanensis.While based on SNP markers,the genetic diversity of H.rhamnoides subsp.sinensis was lower than that of H.rhamnoides subsp.yunnanensis.In this study,the number of SSR marker loci was small and had high variability,so SNP markers were more representative to reflect the variation patterns on the genome.(3)Phylogenetic tree and population structure divided H.rhamnoides subsp.sinensis into two major branches.The two branches correspond to the populations distributed in Qinghai and Gansu on the west side of Qilian Mountains,and the populations distributed in Shaanxi,Shaanxi,Hebei and Inner Mongolia on the east side of Qilian Mountains.Phylogenetic tree and population structure also divided H.rhamnoides subsp.yunnanensis by Hengduan mountains.(4)H.rhamnoides subsp.sinensis spread northward from the eastern margin of the Qinghai-Tibet Plateau,westward to Qinghai and Gansu,and eastward to the Loess Plateau.In the process of diffusion,five functional genes were changed under the influence of climate.These results indicated that there was a significant differentiation level between H.rhamnoides subsp.sinensis and H.rhamnoides subsp.yunnanensis,and the geographical dividing line between the two species was Songpan and Hongyuan area in Sichuan.Both subspecies had population structure,the former is bounded by Qilian Mountains,the latter is bounded by Hengduan Mountains.The diffusion process of H.rhamnoides subsp.sinensis was mainly affected by temperature and precipitation,and some genes were changed due to adaptation,but these need further functional verification.These results are an important theoretical basis for breeding and provide a reference for further research on the adaptive mechanism.