Genome wide association mapping for tocopherol concentration in soybean seeds across multiple environments

Abstract

Tocopherol (Toc) in soybean seeds has value for foods, medicines, cosmetics, and animal husbandry. Soybean breeders and soybean-derived food industries have thus focused on breeding new soybean cultivars with higher seed Toc content. In this study, an association panel consisting of 180 diverse soybean accessions were used to detect quantitative trait nucleotides (QTNs) and scan possible candidate genes based on genome-wide association analysis (GWAS) and high-throughput single-nucleotide polymorphisms (SNP). Approximately 22,611 SNPs were identified using the specific locus amplified fragment sequencing (SLAF-seq) approach and based on minor allele frequencies (MAFs) > 5 %, which spanned 84.10 % of the soybean whole genome. For the three individuals including α-tocopherol (α-Toc), γ- tocopherol (γ-Toc), δ- tocopherol (δ-Toc), and total tocopherol (total Toc) levels, a total of 18 quantitative trait nucleotides (QTNs) distributed on the 18 genomic regions of 10 chromosomes were verified via GWAS. Seven QTNs (rs55811336, rs7975863, rs37094897, rs7097743, rs17125409, rs330000, and rs4730199) could be identified in more than three environments, and the other eleven could be identified in least two environments. A total of 6, 8, 4, and 10 QTNs were novel loci for α-Toc, γ-Toc, δ-Toc, and total Toc, respectively. Nine QTNs (rs37505279, rs37686178, rs36359429, rs6898494, rs7097743, rs17125409, rs10200201, rs21080726, and rs5680781) were associated with more than one Toc component. A total of 216 candidate genes near the 200-kb flanking region of these identified QTNs were identified as potential candidate genes associated with soybean seed Toc levels. Of these genes, Glyma.17G061900 (located near QTN rs4730199 on Chr.17), a homogentisate phytyltransferase 1 that catalytic homogentisate to 2-methyl-6-phyl-1,4-benzoquinol in Toc biosynthesis, was detected through association analysis, haplotype analysis, and expression pattern analysis. The identified QTNs with beneficial alleles and the candidate genes would be valuable for improving Toc levels in soybean seeds and improving the nutritional value of soybean oil.