Abstract: 【Objective】Genetic variation of nine races of maize landrace germplasm in China was revealed via DNA markers. Genetic relationships and population differentiation of these races were also discussed. All the results will provide informative reference for the following researches focused on uncovering formation and evolution of races, and efficient utilization of different races.【Method】In the present study, 55 SSRs covering the whole maize genome were used to assess the genetic diversity of 224 landraces that represent the nine maize races classified previously based on the germplasm preserved in China National GenBank. Three diversity parameters, including the average alleles per locus, gene diversity, and polymorphism information content (PIC), of all these 224 landraces were calculated by the Summary Manu of PowerMarker V3.25. Statistical differences among these diversity parameters of the nine races were determined via Wilcoxon signed-rank test at the same sample size level through resampling strategy. Euclidean distances of these nine races were calculated by the Phylogeny Manu of PowerMarker, and the clustering analysis based on the Euclidean distance was carried out among these races. Analysis of molecular variance (AMOVA) of these nine races was carried out by the Structure Manu, and the F_ST between the race pairs of these nine races was also estimated. 【Result】The diversity results revealed by 55 SSRs showed that the average alleles per locus, gene diversity and PIC were 11.53, 0.6315, and 0.5953, respectively, ranging from 4.42 to 7.64, 0.5788 to 0.6532, and 0.5334 to 0.6117, correspondingly. Though the two races of Southwestern Yellow Flints and Derived Race possessed relatively higher number of alleles per locus, no statistical differences of these three genetic diversity parameters were detected by the resampling strategy within each pair of races (P＞0.05). Nine races were assigned into three clusters, and one cluster was consisted of popcorn race, another cluster was consisted of 3 northern races, and the rest five races including Waxy Race, Derived Race and three southwestern races formed the third cluster. Results from the AMOVA indicated that the molecular variance among races was only 3%, far less than that detected among accessions within races (50%). F_ST of the race pairs ranged from 0.29% to 7.63%, and the F_ST of Southwestern White Flints vs Southern Waxy Race (0.29%), Southwestern Yellow Flints vs Derived Race (0.80%), and Southwestern Dents vs Derived Race (0.70%) were relatively lower than those of the other race pairs.【Conclusion】A total of 634 alleles were detected by 55 SSRs covered the entire maize genome within the nine races, suggesting that abundant genetic variation exists within the germplasm of these nine maize races formed during the long-term artificial and natural selection in China. In addition, the close relationships and relatively lower F_ST of the races or race pairs suggested that Southwestern White Flints might act as the fundamental germplasm base of Southern Waxy Race (F_ST=0.29%). The lowest F_ST of Derived Race vs. the other eight races were observed between the race pairs of Derived Race vs Southwestern Yellow Flints (0.80%) and Derived Race vs Southwestern Dents (0.70%), implying that these two races might play more important roles in the formation and evolution of Derived Race.

Key words: maize (Zea mays L.), race, SSR, genetic variation