Genetic diversity of 169 maize inbred lines with different genetic backgrounds

【Objective】 To analyze the genetic diversity and population genetic structure of different maize inbred lines,which could provide theoretical reference for maize breeding practice in Guangxi. 【Method】 A total of 169 maize inbred lines with different genetic backgrounds were used as materials, with 7 Guangxi backbone inbred lines and 3 backbone inbred lines from other places in China were as control. The whole genome of maize inbred lines was scanned by10K SNP maize chip. The genetic diversity and population genetic structure were analyzed by genetic similarity, phylogeny, principal components and homology identification（IBD）.【Result】 A total of 7565 high-quality and available SNP molecular markers were identified, which were distributed across 10 chromosomes, with an average of 756 markers per chromosome. The detection rate of these markers was all above 97.12%, with an average detection rate of 99.57%. The heterozygosity rate of the 174 maize inbred lines ranged from 0.21% to 7.28%, with an average of 0.86%.Among them, 144 maize inbred lines had a heterozygosity rate not exceeding 1.00%, while the heterozygosity rate of 5 maize inbred lines was relatively high（31.29% to 36.36%）. The genetic similarity among the 174 samples ranged from 0.486 to 0.999, with an average of 0.609. Among these, the 2 southwestern core inbred lines bred in Guangxi, B24（ZNC442） and CK_D2（Guangxi A10341）, had average genetic similarity values of 0.642 and 0.629 with other materials respectively. The phylogenetic tree showed that the 179 maize inbred lines, including 10 reference inbred lines, were divided into 2 major groups: Reid group and the tropical/subtropical group. The Reid group contained 13 inbred lines, accounting for 7.26%,while the tropical/subtropical group contained 166 inbred lines, accounting for 92.74%. The tropical/subtropical group could be further divided into 7 subgroups, with the Suwan group and the CM group being the main ones, containing 56 and 51 inbred lines respectively, accounting for 31.28% and 28.49%. The principal component analysis（PCA） results showed that the clustering of maize inbred lines in PCA1v3 was basically consistent with the clustering results of the phylogenetic tree, clearly distinguishing the Reid group from the tropical/subtropical group. Most inbred lines in the tropical/subtropical group were distributed near the reference inbred lines of the CM group and the Suwan group. The IBD clustering results showed that the Reid group, Suwan group, CM group and A group had 21, 47, 64 and 47 inbred lines respectively. The Venn diagram of phylogenetic analysis, principal component analysis and IBD grouping Venn diagram showed that the number of inbred lines shared by the Reid group, Suwan group,CM group and A group were 12, 35, 18 and 11 respectively. 【Conclusion】 The maize inbred lines in Guangxi have complex origin and similar genetic backgrounds. The classification results obtained from different analytical methods are not entirely consistent. Therefore, it is necessary to integrate breeding practice to conduct group classification. The southwest backbone maize inbred lines ZNC442 and Gui A10341 bred in Guangxi belong to A group. The best mating pattern is A group × Reid group,followed by A group × Suwan group and A group × CM group.