Heinong 84 is one of the major soybean varieties growing in Northeast China, and is resistant to the infection of all strains of soybean mosaic virus (SMV) in the region including the most prevalent strain, N3. However, the resistance gene(s) in Heinong 84 and the resistant mechanism are still elusive. In this study, genetic and next-generation sequencing (NGS)-based bulk segregation analysis (BSA) were performed to map the resistance gene using a segregation population from the cross of Heinong 84 and a susceptible cultivar to strain N3, Zhonghuang 13. Results show that the resistance of Heinong 84 is controlled by a dominant gene on chromosome 13. Further analyses suggest that the resistance gene in Heinong 84 is probably an allele of Rsv1. Finally, two pairs of single-nucleotide-polymorphism (SNP)-based primers that are tightly cosegregated with the resistance gene were designed for rapidly identifying resistant progenies in breeding via the cleaved amplified polymorphic sequence (CAPS) assay.

Soybeans are essential crops that supply protein and oil. The composition and contents of soybean fatty acids are relevant to human health and have a significant relationship with soybean oil processing and applications. Identifying quantitative trait locus (QTL) genes related to palmitic acid could facilitate the development of a range of nutritive soybean cultivars using molecular marker-assisted selection. In this study, we used a cultivar with higher palmitic acid content, ‘Dongnong42’, and a lower palmitic acid content cultivar, ‘Hobbit’, to establish F_2:6 recombinant inbred lines. A high-density genetic map containing 9980 SLAF markers was constructed and distributed across 20 soybean chromosomes. The genetic map contained a total genetic distance of 2602.58 cM and an average genetic distance of 0.39 cM between adjacent markers. Two QTLs related to palmitic acid content were mapped using inclusive composite interval mapping, explaining 4.2–10.1% of the phenotypic variance in three different years and environments, including the QTL included in seed palmitic 7-3, which was validated by developing SSR markers. Based on the SNP/Indel and significant differential expression analyses of Dongnong42 and Hobbit, two genes, Glyma.15g119700 and Glyma.15g119800, were selected as candidate genes. The high-density genetic map, QTLs, and molecular markers will be helpful for the map-based cloning of palmitic acid content genes. These could be used to accelerate breeding for high nutritive value cultivars via molecular marker-assisted breeding.

Phosphorus is an indispensable nutrient for nitrogen metabolism in soybeans. In this study, two P levels were established, 1 mg/L (low-P stress) and 31 mg/L (normal P, CK), by combining ¹⁵N labeling with real-time quantitative PCR and the UHPLC-MS/MS method, to analyze soybean nitrogen accumulation, ¹⁵N abundance, nodule nitrogen fixation accumulation, nodule nitrogen fixation rate, soluble protein content, the relative expression of phosphorus transporters, amino acid changes, and metabolic pathways. The impacts of phosphorus stress on soybean nitrogen metabolism were explored from the perspectives of nitrogen accumulation and protein metabolism. The results demonstrated that low-P stress promoted the absorption of fertilizer nitrogen by aboveground parts, roots, and nodules of soybeans. However, it significantly inhibited nitrogen accumulation (11.09–95.41%), nodule nitrogen fixation accumulation (21.54–96.21%), and nodule nitrogen fixation rate (2.95–37.75%). The soluble protein content in both leaves and nodules decreased remarkably, while the relative expression of GmPT7 was upregulated in leaves, roots, and nodules under low-P stress. A total of 70 amino acids exhibited alterations, among which 26 amino acids were involved in 37 metabolic pathways, playing a crucial role in regulating the effects of low-P stress on soybean nitrogen metabolism. This study identifies significant alterations in nitrogen accumulation, nodule nitrogen fixation, and the expression of phosphorus transporter genes, providing insights into the metabolic pathways involved in soybean’s adaptation to phosphorus deficiency. This research provides a solid theoretical foundation for further in-depth investigations into the physiological and molecular mechanisms of soybean response to low-P stress.

Drought is the main abiotic stress limiting soybean production worldwide and seriously limits the reproductive growth of soybean. To elucidate the molecular mechanisms of drought stress response in soybean seed developmental stages, transcriptome analysis was performed on five seed developmental stages under drought stress and control conditions. Thousands of genes were found to change in expression level under drought stress, GO and KEGG enrichment analysis showed that differentially expressed genes (DEGs) were involved in drought resistance at every stage or tissue, but there were very few DEGs at the primary stage of seed development, which indicated that the seeds at the primary developmental stage were influenced little by drought stress. There was no shared DEG among all five stages or tissues, this indicated that they have different mechanisms to resist drought stress. Furthermore, we investigated DEGs associated with drought response at different stages to identify candidate regulators of drought stress response during soybean seed development. These genes are associated with metabolic and regulatory networks, among others. Taken together, the results will expand our understanding of the adaptation of soybean to drought stress and provide new insights into the molecular mechanisms of soybean drought tolerance development.

Marker-Assisted Selection Strategies for Drought Tolerance in Soybean and Future Perspectives