Chemical compounds in soybean (Glycine max (L.) Merr.) seed have great effects on the flavour and taste of soymilk. The 1-octen-3-ol content in soybean seed could produce sensory off-flavours (mushrooms, lavender, rose and hay flavour) during the processing of soymilk. The most effective way to reduce off-flavours of soymilk is the screening and utilisation of soybean cultivars with reduced 1-octen-3-ol content. However, genomic study of 1-octen-3-ol in soybean has not previously been reported. In the present work, a natural population of 90 diverse soybean accessions was used to dissect the genetic basis of 1-octen-3-ol content in soybean seed through genome-wide association analysis by using 26822 single nucleotide polymorphisms (SNPs). Twenty-one novel quantitative trait nucleotides (QTNs) were thus identified to be associated with 1-octen-3-ol content in soybean seed. Among them, 13 QTNs overlapped with, or were located in, the linked regions of known QTNs for protein, oil and/or fatty acid content in soybean seed. The functional genes located in the 200-kb genomic region of each peak SNP were considered possible candidates related to 1-octen-3-ol, such as genes involved in amino acid metabolism, protein content, and hormone metabolism. The identified loci with beneficial alleles and the candidate genes may be valuable for improving the off-flavours of soymilk.

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Flavour is an essential quality characteristic of soymilk; however, it contains volatile compounds unacceptable to consumers. Hexanal is the most important flavour compound that gives a sensory beany, grassy flavour in the soymilk. An effective way to reduce hexanal content in soymilk is to screen for and utilise cultivars of soybean (Glycine max (L.) Merr.) with lower hexanal content. The objective of the present study was to dissect the genetic basis of hexanal content in soybean seed by using genome-wide association analysis (GWAS), thereby providing guidance for the selection and breeding of soybean varieties with low hexanal content. We used 24651 single-nucleotide polymorphisms (SNPs) and screened seeds from 111 cultivated soybean accessions to identify quantitative trait nucleotides (QTNs) affecting hexanal content. We discovered 14 novel QTNs located on five different chromosomes that are significantly associated with hexanal content in soybean seed. Among these, 11 QTNs co-localised with quantitative trait loci previously found in linkage or association mapping studies related to protein, oil and/or fatty acid content in soybean seed. We also identified some candidate genes involved in amino acid metabolism, protein content, lipid metabolism and hormone metabolism. Six cultivars with low hexanal content were identified by screening. This is the first GWAS study on hexanal content in soybean seed, and a number of QTNs and candidate genes were identified. Some of these may be useful to breeders for the improvement of marker-assisted breeding efficiency for low hexanal content and may be useful for exploring possible molecular mechanisms underlying hexanal content in soybean seed.

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