Abstract
Soybean is a globally important legume crop that provides a primary source of high-quality vegetable protein and oil. Seed protein and oil content are two valuable quality traits controlled by multiple genes in soybean. In this study, the restricted two-stage multi-locus genome-wide association analysis (RTM-GWAS) procedure was performed to dissect the genetic architecture of seed protein and oil content in a diverse panel of 279 soybean accessions from the Yangtze and Huaihe River Valleys in China. We identified 26 quantitative trait loci (QTLs) for seed protein content and 23 for seed oil content, including five associated with both traits. Among these, 39 QTLs corresponded to previously reported QTLs, whereas 10 loci were novel. As reported previously, the QTL on chromosome 20 was associated with both seed protein and oil content. This QTL exhibited opposing effects on these traits and contributed the most to phenotype variation. From the detected QTLs, 55 and 51 candidate genes were identified for seed protein and oil content, respectively. Among these genes, eight may be promising candidate genes for improving soybean nutritional quality. These results will facilitate marker-assisted selective breeding for soybean protein and oil content traits.
Highlights
Soybean (Glycine max (L.) Merr.) is a globally important legume crop, the seed of which contains approximately 40% protein and 20% oil, accounting for 70% of world protein meal and 29% of vegetable oil consumption [1]
The identification of molecular markers associated with quantitative trait loci (QTLs) controlling protein and oil content is a necessary prerequisite for breaking the negative correlations between both the traits [5]
Seed oil content ranged from 15.2% to 21.4% with an average of 18.5% in 2015, and from 14.8% to 21.1% with an average of 18.2% in 2016 (Figure S1B)
Summary
Soybean (Glycine max (L.) Merr.) is a globally important legume crop, the seed of which contains approximately 40% protein and 20% oil, accounting for 70% of world protein meal and 29% of vegetable oil consumption [1]. The phenotypic range of protein content of soybean has been reported to be 34.1–56.8% of seed dry mass, and oil content ranged from 8.3 to 27.9% [3], suggesting that there is great potential for genetic improvement of soybean seed protein and oil content. Breeding cultivated soybean varieties with high-protein and high-oil is an extremely important and promising objective. The negative correlation between protein and oil content make improvement of both traits simultaneously a challenging task using conventional breeding [4]. The identification of molecular markers associated with quantitative trait loci (QTLs) controlling protein and oil content is a necessary prerequisite for breaking the negative correlations between both the traits [5]
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