Genome-wide association analysis reveals zinc-tolerant loci of rapeseed at germination stage

Zinc (Zn) is one of the important mircroelements, but the excessive amount application would affect plant growth and development. Genome-wide association analysis (GWAS) was performed on the relative hypocotyl length (RHL) using the 140 B. napus genotyped under zinc stress treatment (30 mg L^-1) at germination stage by Illumina 60K SNP array, and then significant SNP locus and candidate genes were detected. In the study, the population structure analysis revealed that the 140 B. napus were classified into two subgroups, and the kinship coefficients of the 89% materials were less than 0.1, indicating the tested population had a distant relationship. GWAS analysis indicated that there were significantly 8 SNP locus correlated to RHL, and single SNP loci could give an explanation on the 22.0%–33.2% phenotype variation. The differential expressed gene (DEGs) were detected by RNA-Seq. GO enrichment analysis indicated that the up-regulated genes mainly participated in redox reaction, ion transport, stress response, defense response and sulfur compound transport. Nineteen candidate genes response to zinc stress were identified by GWAS analysis and RNA-seq, including the genes encoding zinc finger protein (B-box type and ZFP1), glutathione transferase GSTU21, peroxidase family protein, ABC and MFS transporters, cell wall-related kinase protein, and genes encoding transcription factors (TF), such as BnaA07g27330D (MYB), BnaA02g30270D (bHLH), BnaA07g27840D (WRKY57), BnaA07g31860D (ORA47), and BnaA07g28000 (NAC). This study laid the foundation for understanding the molecular mechanism of zinc stress in B. napus.