Abstract
BackgroundExploring genetic differentiation and genomic variation is important for both the utilization of heterosis and the dissection of the genetic bases of complex traits.MethodsWe 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.ResultsWe 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.ConclusionsHere 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0646-7) contains supplementary material, which is available to authorized users.
Highlights
Exploring genetic differentiation and genomic variation is important for both the utilization of heterosis and the dissection of the genetic bases of complex traits
The results indicated that 1,000 singlenucleotide polymorphisms (SNPs) might be sufficient for population structure analyses
A second peak of ΔK emerged at k = 4 (Fig. 1a), indicating that this panel could be further divided into four subgroups: Stalk Synthetic (SS), Non-Stiff Stalk (NSS), Modified Introduction in China (MICN), and TS I (Fig. 1b k = 4)
Summary
Exploring genetic differentiation and genomic variation is important for both the utilization of heterosis and the dissection of the genetic bases of complex traits. The aforementioned studies provided useful information for both heterosis utilization and the dissection of the genetic basis for complex traits, but the accessions used in previous studies were obtained from a single geographical origin and have relied on the smallest number of markers, which limits our understanding of genetic differentiation. The development of high-throughput genotyping strategies has facilitated the study of historical genetic changes in maize [21,22,23] Another large natural panel of 2,815 maize accessions was investigated using the genotyping by sequencing (GBS) method [12], and this study provided abundant information about pair relationships of accessions and identified many new genetic loci associated with flowering time (FT)-related traits. Five subpopulations were observed in this paper; the distance between SS and NSS subpopulations was small, which indicated a slight bias when comparing with previous studies and the knowledge of maize pedigrees based on breeding practice [10, 22, 24,25,26]
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