Analysis of genetic differentiation and genomic variation to reveal potential regions of importance during maize improvement.
BACKGROUND
Exploring genetic differentiation and genomic variation is important for both the utilization of heterosis and the dissection of the genetic bases of complex traits.


METHODS
We integrated 1857 diverse maize accessions from America, Africa, Europe and Asia to investigatetheir genetic differentiation, genomic variation using 43,252 high-quality single-nucleotide polymorphisms(SNPs),combing GWAS and linkage analysis strategy to exploring the function of relevant genetic segments.


RESULTS
We uncovered many more subpopulations that recently or historically formed during the breeding process. These patterns are represented by the following lines: Mo17, GB, E28, Ye8112, HZS, Shen137, PHG39, B73, 207, A634, Oh43, Reid Yellow Dent, and the Tropical/subtropical (TS) germplasm. A total of 85 highly differentiated regions with a DEST of more than 0.2 were identified between the TS and temperate subpopulations. These regions comprised 79% of the genetic variation, and most were significantly associated with adaptive traits. For example, the region containing the SNP tag PZE.108075114 was highly differentiated, and this region was significantly associated with flowering time (FT)-related traits, as supported by a genome-wide association study (GWAS) within the interval of FT-related quantitative trait loci (QTL). This region was also closely linked to zcn8 and vgt1, which were shown to be involved in maize adaptation. Most importantly, 197 highly differentiated regions between different subpopulation pairs were located within an FT- or plant architecture-related QTL.


CONCLUSIONS
Here we reported that 700-1000 SNPs were necessary needed to robustly estimate the genetic differentiation of a naturally diverse panel. In addition, 13 subpopulations were observed in maize germplasm, 85 genetic regions with higher differentiation between TS and temperate maize germplasm, 197 highly differentiated regions between different subpopulation pairs, which contained some FT- related QTNs/QTLs/genes supported by GWAS and linkage analysis, and these regions were expected to play important roles in maize adaptation.
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China. wuxunyong@126.com.|Nanchong Academy of Agricultural Sciences, Nanchong, Sichuan, China. wuxunyong@126.com.
Xun
X
Wu
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China. yongxiangli@163.com.
Yongxiang
Y
Li
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China. liyu03@caas.cn.
Xin
X
Li
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China.
Chunhui
C
Li
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China.
Yunsu
Y
Shi
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China.
Yanchun
Y
Song
Nanchong Academy of Agricultural Sciences, Nanchong, Sichuan, China.
Zuping
Z
Zheng
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China. liyu03@caas.cn.
Yu
Y
Li
Institute of Crop Science, Chinese Academy of Agricultural Science, Beijing, China. wangtianyu@caas.cn.
Tianyu
T
Wang
D016000:Cluster Analysis; D060146:Ecotype; D035264:Flowers / Q000502:physiology; D014644:Genetic Variation; D005828:Genetics, Population; D018745:Genome, Plant; D055106:Genome-Wide Association Study; D008957:Models, Genetic; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D003313:Zea mays / Q000235:genetics*