Abstract: 【Objective】The objective of this study is to analyze the genetic diversity and relationship of broomcorn millet landraces and wild materials by SSR markers, to provide available data for further evolutionary study of broomcorn millet.【Method】137 SSR primers are used to identify polymorphisms in six representatives which selected randomly from the total of accessions. A total of 103 primers produce clear and reproducible polymorphic fragments among the six accessions and then are used to amplify 146 broomcorn millet accessions. Genetic diversity and relationship between different individuals and populations is evaluated by analyzing genetic parameter, clustering, and genetic structure.【Result】 103 SSR markers detect a total of 308 alleles (Na) with an average of 2.99 for each SSR and the mean values of Shannon-Weaver index (I), Nei and PIC were 0.8478, 0.3642 and 0.5544, respectively. Their resolution range was 0.334-4.002 and more than 60% distribution at intervals of 1-4, indicated the moderate resolving power of these SSR. The observed number of alleles (2.9126), Shannon-Weaver index (0.8302), expected heterozygosity (0.5023), and PIC value (0.5278) of broomcorn millet accessions in China were all higher than those in abroad, indicated more abundant genetic diversity in Chinese samples. The genetic distance of the 12 populations ranged from 0.0783 to 0.5762 with a mean of 0.2938. The genetic identity ranged from 0.5620 to 0.9247 with a mean of 0.75. We found that the genetic similarity had a certain correlation with geographical distribution. The closer geographical distribution, the smaller genetic distance, the higher genetic identity. Cluster analysis divided 12 populations into 4 groups at a genetic distance of 0.15. Among them, resources in South America and Shanxi were each independently divided into one group, which had a far-distance relationship with other resources. In the inter-individual clustering, the division of resources at home and abroad was very significant. At a genetic distance of 0.63, 146 broomcorn millet accessions could be divided into three groups. Group Ⅰand group Ⅱ were foreign accessions, and group Ⅲ was domestic accessions. Further, group Ⅱ was divided into three subpopulations at a genetic distance of 0.39, and group Ⅲ was divided into five subpopulations at a genetic distance of 0.45. There had closer genetic relationship between Asia and European resources, as well as Hebei, Shanxi and Inner Mongolia in China resources than other populations. The result of genetic structure analysis showed that there is obvious genetic differentiation between the domestic populations and foreign populations. Five groups (Group 2, Group 5, Group 6, Group 7 and Group 9) were unique genotypes which owned by Chinese wild resources and distributed more widely, 2 groups (Group 1 and Group 4) were unique genotypes of foreign resources and have a relative narrow distribution. The population structures of Ningxia and South America tend to be independent, and the population structures of Hebei, Heilongjiang and Asia tend to be diversified. The UPGMA clustering results were consistent with the results of genetic structure analysis, and the genetic relationships were related to their geographical distribution.【Conclusion】The genetic diversity of wild accessions is higher than that of landraces, of which Hebei population has the most abundant genetic diversity, so we suppose Hebei province may be the sub-origin center of broomcorn millet.

Key words: Panicum miliaceum L, wild broomcorn millet, foreign germplasm, SSR markers, genetic diversity, population structure