Abstract
BackgroundIncreasing rice (Oryza sativa L.) yield is a crucial challenge for modern agriculture. The ideal plant architecture is considered to be critical to enhance rice yield. Elite plant morphological traits should include compact plant type, short stature, few unproductive tillers, thick and sturdy stems and erect leaves. To reveal the genetic variations of important morphological traits, 523 germplasm accessions were genotyped using the Illumina custom-designed array containing 5,291 single nucleotide polymorphisms (SNPs) and phenotyped in two independent environments. Genome-wide association studies were performed to uncover the genotypic and phenotypic variations using a mixed linear model.ResultsIn total, 126 and 172 significant loci were identified and these loci explained an average of 34.45 % and 39.09 % of the phenotypic variance in two environments, respectively, and 16 of 298 (~5.37 %) loci were detected across the two environments. For the 16 loci, 423 candidate genes were predicted in a 200-kb region (±100 kb of the peak SNP). Expression-level analyses identified four candidate genes as the most promising regulators of tiller angle. Known (NAL1 and Rc) and new significant loci showed pleiotropy and gene linkage. In addition, a long genome region covering ~1.6 Mb on chromosome 11 was identified, which may be critical for rice leaf architecture because of a high association with flag leaf length and the ratio of flag leaf length and width. The pyramid effect of the elite alleles indicated that these significant loci could be beneficial for rice plant architecture improvements in the future. Finally, 37 elite varieties were chosen as breeding donors for further rice plant architectural modifications.ConclusionsThis study detected multiple novel loci and candidate genes related to rice morphological traits, and the work demonstrated that genome-wide association studies are powerful strategies for uncovering the genetic variations of complex traits and identifying candidate genes in rice, even though the linkage disequilibrium decayed slowly in self-pollinating species. Future research will focus on the biological validation of the candidate genes, and elite varieties will also be of interest in genome selection and breeding by design.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2245-2) contains supplementary material, which is available to authorized users.
Highlights
Increasing rice (Oryza sativa L.) yield is a crucial challenge for modern agriculture
The array consisted of 5,291 single nucleotide polymorphisms (SNPs) that were chosen from the Rice Haplotype Map Project Database [27]
4,136 SNPs of high genotyping quality were used for the Genome-wide association study (GWAS) analysis (Additional file 3: Table S2)
Summary
Increasing rice (Oryza sativa L.) yield is a crucial challenge for modern agriculture. Elite plant morphological traits should include compact plant type, short stature, few unproductive tillers, thick and sturdy stems and erect leaves. Plant morphological traits have important effects on rice yield, and elite plant architecture should include short stature, few unproductive tillers, thick and sturdy stems, more grains per panicle and erect leaves [1]. These traits are controlled by multiple quantitative loci. A classic gene, NAL1 with pleiotropic effects on multiple traits, including polar auxin transport and vascular patterns, was characterized on chromosome 4 [11,12,13,14]. QPE9-1 [20] and EP2 [21] were two erect panicle QTLs, and sp leads to a short-panicle phenotype [22]
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