Abstract: 【Objective】 Understanding the genetic diversity and population structure of representative maize accessions are of importance in breeding practice for the guidance and reference. 【Method】A total of 344 maize inbred lines were selected, including American heterotic group, local germplasm, New germplasm used in maize breeding in China in recent years which were broadly representative. These lines were genotyped by 3 072 SNP markers which were developed by Maize Research Center, BAAFS to reveal the genetic diversity and population structure. 【Result】For 3 072 high-quality SNPs, the gene diversity averaged 0.442, ranging from 0.028 to 0.646, and the PIC averaged 0.344, ranging from 0.028 to 0.570. The result of population structure based on a model-based method indicated that these 344 lines could be divided into eight groups, including Lüda red cob, Huangzaosi improved lines, Iodent, Lancaster, P group, Improved Reid group, Reid and X group. The seven groups above were well-known, and the X group was selected from the populations constructed from X1132X. Among the eight groups, the Fst ranged from 0.319 to 0.512, and the genetic distance ranged from 0.229 to 0.514. AMOVA results indicated that 38.6% of the total genetic variation occurred among groups, 58.1% within groups and 3.3% within lines. PCA results showed that X group had higher genetic differentiation with Huangzaosi improved lines and Lancaster, but lower with Iodent. The genetic diversity of subpopulations indicated that with the increase of breeding years, the average of genetic diversity in each subpopulation was decreased, and among them, X group had the highest genetic diversity. Further analysis showed that the genetic diversity of core accessions in American heterotic group and local germplasm were higher decreased compared with that in P group and Improved Reid group. However, the genetic diversity of core accessions in X group was no decreased, which indicated that the core accessions of X group still maintained higher genetic diversity and had potential application in breeding.【Discussion】X group was different from the other seven known groups, which can be defined as an independent group. Furthermore, X group had further genetic relationship with Huangzaosi improved lines which indicated the strong heterosis pattern of "X group × Huangzaosi improved lines" had application potential.

Key words:  maize, inbred lines, X group, gene diversity, population structure