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Soybean is an important economic crop in the world, which provides plant protein, oil and a variety of active substances beneficial to human health. In order to comprehensively identify the quality characters of soybean resources abundant in China, 16 kinds of seed quality traits of 520 soybean germplasms in Huang-Huai-Hai ecoregion were evaluated in 6 environments across 2 years with reference to the national standard method. The results showed that the genetic variations of the tested seed quality traits were abundant in the soybean germplasms, and the variation coefficients of isoflavone and tocopherol contents were relative high, while the variation coefficients of protein, oil and fatty acid components were relatively low. Meanwhile, there were significant correlations among the 16 seed quality traits. Principal component analysis showed that the 16 quality traits could be attributed to 5 principal components. Based on the results of principal component analysis, 520 germplasms could be divided into 3 categories by cluster analysis with significant differences. Based on the above results and high stability coefficient analysis, 35 germplasms with multiple or single elite seed quality traits were screened out, which provided important resources for genetic improvement of seed quality traits in soybean. [ABSTRACT FROM AUTHOR]

Chlorophyll is an essential pigment for plant photosynthesis. Drought tolerance affects chlorophyll synthesis, reduces photosynthetic efficiency, and decreases soybean yield. In order to explore the genetic loci of chlorophyll content in soybean under drought stress, drought resistance index (DRI) were calculated by chlorophyll contents under drought and well-watered conditions. Moreover, based on the DRI and re-sequenced genotypes of the soybean natural population (199 accessions) at 20x sequencing depth, the genome-wide association study (GWAS) was performed. The results showed that 237 single nucleotide polymorphisms (SNPs) in 18 loci on the chromosomes 1, 2, 3, 7, 10, 16, 17 and 18 were identified to associate with DRI. Moreover, 181 SNPs (76.37% of the total) were located on chromosome 16, of which 9 SNPs were located in the gene introns, 17 in exons, 21 in upstream or downstream, and 1 in 3' UTR. Based on these, 57 candidate genes flanking the associated SNPs were found, and according to the gene annotation, SNP mutation, and RNA expression, 3 candidate genes, Glyma.16G063600 (F-box protein), Glyma. 10G007000 (AP2-EREBP), and Glyma. 17G143900 (AP2/ERF) were screened out which might be responsible for the drought tolerance in soybean. Above results provided important theoretical foundation for drought tolerance genetic improvement in soybean. [ABSTRACT FROM AUTHOR]

Sugars are always transported to the other organs via sugar transporters to play their important functions in plants. SWEET (sugars will eventually be exported transporters) is a kind of sugar transporters which plays important function in plant growth and development as well as in resistance or tolerance to diverse biotic and abiotic stresses. To analyze the expressions of SWEET genes during pod and seed developments and under different stress conditions in soybean, the SWEET genes were firstly analyzed based on the newly published cultivated and wild soybean genomes in the present study. Subsequently, the gene expressions were evaluated during pod and seed developments, as well as in resistance to soybean mosaic virus (SMV) and tolerance to low phosphorus. The results showed that 48 SWEET genes were identified in the cultivated soybean genome (Wm82a4v1), which encoded protein with length 174~354 amino acids and located on 15 chromosomes. Meanwhile, 51 SWEET genes were identified in the wild soybean genome (W05), which encoded length of 84~392 amino acids and located on 16 chromosomes. The phylogenetic tree of SWEET genes in cultivated and wild soybeans showed that they were clustered into 3 sub-groups. Moreover, 16 SWEET genes were expressed in soybean pods with the expressions of Glyma. 06G122200, Glyma. 14G159900 and Glyma. 14G160100 etc. increased during the pod development process. 12 SWEET genes were expressed in soybean seeds, and the expressions of Glyma.08G025100, Glyma.13G041300 and Glyma.14G120300 were increased during the seed development, suggesting their important roles for soybean seed development. The SWEET genes showed different expressions after the inoculation of SMV, and the expressions of Glyma.08G009900 and Glyma.13G264400 were induced in leaves of resistant variety, while had no change in the sensitive variety, implying that they might involve in SMV resistance. The expressions of Glyma.04G198400, Glyma.14G160100 and Glyma.15G211800 were induced in soybean roots after low phosphorus treatment, indicating their important functions in the tolerance to low phosphorus stress. In addition, the single nucleotide polymorphism(SNP)analysis of SWEET genes showed that 43 genes contained 220 nonsynonymous SNPs with 103 located in the conserved domains of encoding proteins. Thus, above results provided candidate genes for molecular breeding of soybean pod and seed yield and diverse stress resistances. [ABSTRACT FROM AUTHOR]

Soybean is an important crops in the world due to its high seed protein and oil contents, while the contents of seed protein and oil attributed to the quantitative traits which were controlled by multiple minor-genes. Though there were many related QTLs reported, most of them only focused on the single additive QTLs, and few of them payed attentions to the epistatic QTLs. In this paper, a soybean RIL population (ZL) was used to study the epistatic QTLs of seed protein and oil contents by analyzing ZL population using Illumina BARCSoySNP6K Beadchip and detecting the phenotypes under four different environments. The results showed that there were 48 pairs of epistatic QTLs associated with protein content and 55 pairs of epistatic QTLs related to oil content in soybean seeds. Furthermore, there were 19 pairs of co-located epistatic QTLs controlling the protein and oil contents simultaneously. Among these co-located epistatic QTLs, 12 pairs of them shared the same QTL mapping regions, 2 pairs of them shared one same marker and five pairs of them had the QTLs regions not above 5 cM genetic distance, which could be regarded as the same QTL. Meanwhile, the results also showed that these epistatic QTLs located on nineteen chromosomes of soybean except for the chromosome 11. Thus, this study identified many epistatic QTLs for soybean seed protein and oil contents, which not only could be used for soybean quality genetic improvements in future, but also offered some evidences for reveal the negative relationships between seed protein and oil contents in soybean. [ABSTRACT FROM AUTHOR]