Soybean Resistance Research Articles

Soybean hypocotyl elongation is regulated by a MYB33-SWEET11/21-GA2ox8c module involving long-distance sucrose transport.

The length of hypocotyl affects the height of soybean and lodging resistance, thus determining the final grain yield. However, research on soybean hypocotyl length is scarce, and the regulatory mechanisms are not fully understood. Here, we identified a module controlling the transport of sucrose, where sucrose acts as a messenger moved from cotyledon to hypocotyl, regulating hypocotyl elongation. This module comprises four key genes, namely MYB33, SWEET11, SWEET21 and GA2ox8c in soybean. In cotyledon, MYB33 is responsive to sucrose and promotes the expression of SWEET11 and SWEET21, thereby facilitating sucrose transport from the cotyledon to the hypocotyl. Subsequently, sucrose transported from the cotyledon up-regulates the expression of GA2ox8c in the hypocotyl, which ultimately affects the length of the hypocotyl. During the domestication and improvement of soybean, an allele of MYB33 with enhanced abilities to promote SWEET11 and SWEET21 has gradually become enriched in landraces and cultivated varieties, SWEET11 and SWEET21 exhibit high conservation and have undergone a strong purified selection and GA2ox8c is under a strong artificial selection. Our findings identify a new molecular pathway in controlling soybean hypocotyl elongation and provide new insights into the molecular mechanism of sugar transport in soybean.

Transcription factor GmAlfin09 regulates endoplasmic reticulum stress in soybean via peroxidase GmPRDX6.

Soybean (Glycine max [L.] Merr.) is a valuable oil crop but is also highly susceptible to environmental stress. Thus, developing approaches to enhance soybean stress resistance is vital to soybean yield improvement. In previous studies, transcription factor Alfin has been shown to serve as an epigenetic regulator of plant growth and development. However, no studies on Alfin have yet been reported in soybean. In this study, the endoplasmic reticulum (ER) stress- and reactive oxygen species (ROS)-related GmAlfin09 was identified. Screening of genes co-expressed with GmAlfin09 unexpectedly led to the identification of soybean peroxidase 6 (GmPRDX6). Further analyses revealed that both GmAlfin09 and GmPRDX6 were responsive to ER stress, with GmPRDX6 localizing to the ER under stress. Promoter binding experiments confirmed the ability of GmAlfin09 to bind to the GmPRDX6 promoter directly. When GmAlfin09 and GmPRDX6 were overexpressed in soybean, enhanced ER stress resistance and decreased ROS levels were observed. Together, these findings suggest that GmAlfin09 promotes the upregulation of GmPRDX6, and GmPRDX6 subsequently localizes to the ER, reduces ROS levels, promotes ER homeostasis, and ensures the normal growth of soybean even under ER stress. This study highlights a vital target gene for future molecular breeding of stress-resistant soybean lines.

Identification of New Isolates of Phytophthora sojae and Selection of Resistant Soybean Genotypes.

Phytophthora root and stem rot (PRR), caused by Phytophthora sojae, can occur at any growth stage under poorly drained and humid conditions. The expansion of soybean cultivation in South Korean paddy fields has increased the frequency of PRR outbreaks. This study aimed to identify four P. sojae isolates newly collected from domestic fields and evaluate race-specific resistance using the hypocotyl inoculation technique. The four isolates exhibited various pathotypes, with GJ3053 exhibiting the highest virulence complexity. Two isolates, GJ3053 and AD3617, were screened from 205 soybeans, and 182 and 190 genotypes (88.8 and 92.7%, respectively) were susceptible to each isolate. Among these accessions, five genotypes resistant to both isolates were selected. These promising genotypes are candidates for the development of resistant soybean cultivars that can effectively control PRR through gene stacking.

Genetic Diversity and Pathogenicity of the Fusarium Species Complex on Soybean in Serbia.

Using morphological and cultural characteristics for identification, 36 Fusarium isolates were recovered from diseased roots, stems, and seeds of soybean from several localities throughout Vojvodina Province, Serbia. Based on molecular characterization, 12 Fusarium species were identified: F. acuminatum, F. avenaceum, F. commune, F. equiseti, F. graminearum, F. incarnatum, F. oxysporum, F. proliferatum, F. solani, F. sporotrichioides, F. subglutinans, and F. tricinctum. The elongation factor 1-α-based phylogeny grouped the isolates into 12 well-supported clades, but polymorphisms among sequences in some clades suggested the use of the species complex concept: (i) F. incarnatum-equiseti species complex (FIESC)-F. incarnatum and F. equiseti; (ii) F. oxysporum species complex (FOSC)-F. oxysporum; (iii) F. solani species complex (FSSC)-F. solani; and (iv) F. acuminatum/F. avenaceum/F. tricinctum species complex (FAATSC)-F. acuminatum, F. avenaceum, and F. tricinctum. Pathogenicity tests showed that the most aggressive species causing soybean seed rot were F. sporotrichioides, F. graminearum, FIESC, and F. avenaceum. Furthermore, F. subglutinans, FSSC, and F. proliferatum showed a high percentage of pathogenicity on soybean seeds (80 to 100%), whereas variability in pathogenicity occurred within isolates of F. tricinctum. FOSC, F. commune, and F. acuminatum had the lowest pathogenicity. To our knowledge, this is the first study of the characterization of Fusarium species on soybean in Serbia. This study provides valuable information about the composition of Fusarium species and pathogenicity that will be used in further research on soybean resistance to Fusarium-based diseases.

Identification of soybean mosaic virus strain SC7 resistance loci and candidate genes in soybean [Glycine max (L.) Merr.

Soybean [Glycine max (L.) Merr.] is an important legume crop worldwide, which provides abundant plant protein and oil for human beings. Soybean mosaic virus (SMV) can cause serious damage to the yield and quality of soybean, but it is difficult to control SMV with chemicals, breeding SMV-resistant varieties has become the most effective way to control the disease. Therefore, it is important to identify SMV resistance genes from soybean resources and apply them to soybean breeding. In this study, the disease rates (DRs) of 219 soybean accessions to SMV strain SC7 in two environments were investigated. A high-density NJAU 355K SoySNP array was used for genome-wide association study (GWAS) of DR. A 274kb region on chromosome 15 (1,110,567bp to 1,384,173bp) was repeatedly detected in two environments. Six new significant single nucleotide polymorphisms (SNPs) on chromosome 15 were identified. Four of these six SNPs were located within two candidate genes, Glyma.15G015700 and Glyma.15G015800. The elite haplotype Glyma.15G015700Hap I with low DR exhibited strong resistance to SC7. The expression of Glyma.15G015700 in the SMV-resistant accession increased significantly after inoculation with SC7. Furthermore, most of the proteins predicted to interact with Glyma.15G015700 are heat shock proteins, which have been shown to be related to disease resistance. In summary, new SMV resistance loci and a new candidate gene, Glyma.15G015700, were identified and might be utilized in further soybean disease resistance breeding.

Isolates of Corynespora cassiicola, Causal Agent of Target Spot of Soybean, in Kentucky Contain the G143A Mutation Conferring Resistance to Quinone Outside Inhibitor Fungicides

Target spot, caused by Corynespora cassiicola, is a soybean disease of increasing importance in the southern United States. Recently, isolates of C. cassiicola with resistance to quinone outside inhibitor (QoI) fungicides have been confirmed with the G143A mutation in multiple southern states, including Alabama, Arkansas, Mississippi, and Tennessee. From 2017 to 2019, a total of 84 isolates of C. cassiicola were recovered from soybean field in 12 counties in Kentucky. DNA sequencing of the cytochrome b gene of these isolates revealed that 15.5% of the isolates had the G143A mutation that confers resistance to QoI fungicides and were in 50% of the counties in which isolates originated. This represents the first report of QoI fungicide resistance in C. cassiicola isolates from Kentucky soybean fields. Considering these findings, Kentucky soybean growers should adopt target spot management practices which include rotating to non-host crops, planting resistant soybean cultivars, and applying fungicides from different fungicide classes.

Deciphering genetic factors contributing to enhanced resistance against Cercospora leaf blight in soybean (Glycine max L.) using GWAS analysis.

Cercospora leaf blight (CLB), caused by Cercospora cf. flagellaris, C. kikuchii, and C. cf. sigesbeckiae, is a significant soybean [Glycine max (L.) Merr.] disease in regions with hot and humid conditions causing yield loss in the United States and Canada. There is limited information regarding resistant soybean cultivars, and there have been marginal efforts to identify the genomic regions underlying resistance to CLB. A Genome-Wide Association Study was conducted using a diverse panel of 460 soybean accessions from maturity groups III to VII to identify the genomic regions associated to the CLB disease. These accessions were evaluated for CLB in different regions of the southeastern United States over 3years. In total, the study identified 99 Single Nucleotide Polymorphism (SNPs) associated with the disease severity and 85 SNPs associated with disease incidence. Across multiple environments, 47 disease severity SNPs and 23 incidence SNPs were common. Candidate genes within 10kb of these SNPs were involved in biotic and abiotic stress pathways. This information will contribute to the development of resistant soybean germplasm. Further research is warranted to study the effect of pyramiding desirable genomic regions and investigate the role of identified genes in soybean CLB resistance.

Biochemical characterization and metabolic reprogramming of amino acids in Soybean roots under drought stress.

Amino acids play important roles in stress resistance, plant growth, development, and quality, with roots serving as the primary organs for drought response. We conducted biochemical and multi-omics analyses to investigate the metabolic processes of root amino acids in drought-resistant (HN44) and drought-sensitive (HN65) soybean (Glycine max) varieties. Our analysis revealed an increase in total amino acid content in both varieties, with phenylalanine, proline, and methionine accumulating in both. Additionally, several amino acids exhibited significant decreases in HN65 but slight increases in HN44. Multi-omics association analysis identified 13 amino acid-related pathways. We thoroughly examined the changes in genes and metabolites involved in various amino acid metabolism/synthesis and determined core genes and metabolites through correlation networks. The phenylalanine, tyrosine, and tryptophan metabolic pathways and proline, glutamic acid and sulfur-containing amino acid pathways were particularly important for drought resistance. Some candidate genes, such as ProDH and P4HA family genes, and metabolites, such as O-acetyl-L-serine, directly affected up- and downstream metabolism to induce drought resistance. This study provided a basis for soybean drought resistance breeding.

Mesoporous silica entrapped alpha-mangostin constructed tough, high strength, and mildew resistant soybean protein adhesives by organic–inorganic strategy

The production of value-added products from agricultural raw materials has been deemed a cutting-edge approach to attaining an uncontaminated geosphere globally. Thus, soybeans have recently attracted several wood-bonding capability studies due to their biobased, high-performance, and sustainable attributes. However, simultaneously achieving high-performance, mechanical, and anti-mildew properties in soybean protein (SBP) adhesive remains an enormous quest. Herein, an organic–inorganic strategy is reported to formulate SBP adhesive via adipic acid hydrazide strengthened α-mangostin (Sα-M) entrapped by mesoporous silica nanoparticles (MSN), yielding a highly biocompatible dense network (MSN/Sα-M). Afterward, the MSN/Sα-M was incorporated into SBP molecular chains through the enhanced dynamic covalent conjugation and intermolecular sacrificial hydrogen bonds to form SBP@MSN/Sα-M adhesive. Consequently, the multiple synergistic interactions resulted in tough adhesive layers, exhibiting high wood-bonding strength of 2.59 and 1.50 MPa at dry and wet conditions, increasing 66% and 206%, respectively. The SBP@MSN/Sα-M adhesive also offers excellent anti-mildew properties, with an extended wood bonding capability beyond 20 days of storage. This unique, versatile, and sustainable strategy provides new headway for developing bio-based wood adhesives from agricultural raw materials.

A DIRIGENT Gene GmDIR26 Regulates Pod Dehiscence in Soybean.

Pod dehiscence brings much loss for modern agricultural production, and multiple pod dehiscence components have been identified in many plant species. However, the pod dehiscence regulation factors in soybean are limited. In this study, we investigate the function of GmDIR26, a close homologues gene of pod dehiscence genes GmPdh1, PvPdh1, and CaPdh1, in the regulation of pod dehiscence in soybean. The secondary and tertiary structure analysis reveals that GmDIR26 protein has a similar structure with GmPdh1, PvPdh1, and CaPdh1 proteins. Synteny analysis of soybean and chickpea genomes shows that the genomic region surrounding GmDIR26 and CaPdh1 might be evolved from the same ancestor, and these two genes might have similar function. GmDIR26 shows an increased expression pattern during pod development and reaches a peak at beginning seed stage. Meanwhile, GmDIR26 exhibits high expression levels in dorsal suture and pod wall, but low expression pattern in ventral suture. In addition, GmDIR26 shows higher expression levels in pod dehiscence genotype than that in pod indehiscence accessions. Overexpression of GmDIR26 in soybean increases pod dehiscence in transgenic plants, of which the lignin layer in inner sclerenchyma pods is thicker and looser. The expression levels of several pod dehiscence genes are altered. Our study provides important information for further modification of pod dehiscence resistance soybean and characterization of soybean pod dehiscence regulation network.

Long noncoding RNAs underlie multiple domestication traits and leafhopper resistance in soybean.

The origin and functionality of long noncoding RNA (lncRNA) remain poorly understood. Here, we show that multiple quantitative trait loci modulating distinct domestication traits in soybeans are pleiotropic effects of a locus composed of two tandem lncRNA genes. These lncRNA genes, each containing two inverted repeats, originating from coding sequences of the MYB genes, function in wild soybeans by generating clusters of small RNA (sRNA) species that inhibit the expression of their MYB gene relatives through post-transcriptional regulation. By contrast, the expression of lncRNA genes in cultivated soybeans is severely repressed, and, consequently, the corresponding MYB genes are highly expressed, shaping multiple distinct domestication traits as well as leafhopper resistance. The inverted repeats were formed before the divergence of the Glycine genus from the Phaseolus-Vigna lineage and exhibit strong structure-function constraints. This study exemplifies a type of target for selection during plant domestication and identifies mechanisms of lncRNA formation and action.

Effects of narrow-wide row planting patterns on canopy photosynthetic characteristics, bending resistance and yield of soybean in maize‒soybean intercropping systems

With the improvements in mechanization levels, it is difficult for the traditional intercropping planting patterns to meet the needs of mechanization. In the traditional maize‒soybean intercropping, maize has a shading effect on soybean, which leads to a decrease in soybean photosynthetic capacity and stem bend resistance, resulting in severe lodging, which greatly affects soybean yield. In this study, we investigated the effects of three intercropping ratios (four rows of maize and four rows of soybean; four rows of maize and six rows of soybean; six rows of maize and six rows of soybean) and two planting patterns (narrow-wide row planting pattern of 80–50 cm and uniform-ridges planting pattern of 65 cm) on soybean canopy photosynthesis, stem bending resistance, cellulose, hemicellulose, lignin and related enzyme activities. Compared with the uniform-ridge planting pattern, the narrow-wide row planting pattern significantly increased the LAI, PAR, light transmittance and compound yield by 6.06%, 2.49%, 5.68% and 5.95%, respectively. The stem bending resistance and cellulose, hemicellulose, lignin and PAL, TAL and CAD activities were also significantly increased. Compared with those under the uniform-ridge planting pattern, these values increased by 7.74%, 3.04%, 8.42%, 9.76%, 7.39%, 10.54% and 8.73% respectively. Under the three intercropping ratios, the stem bending resistance, cellulose, hemicellulose, lignin content and PAL, TAL, and CAD activities in the M4S6 treatment were significantly greater than those in the M4S4 and M6S6 treatments. Compared with the M4S4 treatment, these variables increased by 12.05%, 11.09%, 21.56%, 11.91%, 18.46%, 16.1%, and 16.84%, respectively, and compared with the M6S6 treatment, they increased by 2.06%, 2.53%, 2.78%, 2.98%, 8.81%, 4.59%, and 4.36%, respectively. The D-M4S6 treatment significantly improved the lodging resistance of soybean and weakened the negative impact of intercropping on soybean yield. Therefore, based on the planting pattern of narrow-wide row maize‒soybean intercropping planting pattern, four rows of maize and six rows of soybean were more effective at improving the lodging resistance of soybean in the semiarid region of western China.

A pair of atypical NLR-encoding genes confers Asian soybean rust resistance in soybean

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is a devastating disease that is present in all major soybean-producing regions. The limited availability of resistant germplasm has resulted in a scarcity of commercial soybean cultivars that are resistant to the disease. To date, only the Chinese soybean landrace SX6907 has demonstrated an immune response to ASR. In this study, we present the isolation and characterization of Rpp6907-7 and Rpp6907-4, a gene pair that confer broad-spectrum resistance to ASR. Rpp6907-7 and Rpp6907-4 encode atypic nucleotide-binding leucine-rich repeat (NLR) proteins that are found to be required for NLR-mediated immunity. Genetic analysis shows that only Rpp6907-7 confers resistance, while Rpp6907-4 regulates Rpp6907-7 signaling activity by acting as a repressor in the absence of recognized effectors. Our work highlights the potential value of using Rpp6907 in developing resistant soybean cultivars.

Fortify the defense frontline: MAPKs phosphorylate receptor-like cytoplasmic kinase to maintain plant resistance in soybean

Mitogen-activated protein kinase (MAPK) activation is one of the significant immune events that respond to pathogens in plants. A MAPK cascade often contains a MAPK kinase kinase (MAPKKK), a MAPK kinase (MAPKK/MKK), and a MAPK. The well-characterized MAPK cascade, to date, is the MAPKKK3/4/5-MKK4/5-MPK3/6 module. Soybean cyst nematodes (SCN) is one of the most devastating soybean pathogens. However, the early immune components contributing to soybean resistance to SCN and the role of the MAPK cascade in the soybean–SCN interaction remain unclear. A recent study published in Plant Cell discovered that GmMPK3/6 phosphorylates a receptor-like cytoplasmic kinase (RLCK), CDG1-LIKE1 (GmCDL1), and maintains the stability of GmCDL1 in soybean. Remarkably, GmCDL1 enhances GmMPK3/6 activation and resistance to SCN by phosphorylating GmMAPKKK5 and activating the GmMAPKKK5-GmMKK4-GmMPK3/6 cascade. In addition, two L-type lectin receptor kinases (LecRKs), GmLecRK02g and GmLecRK08g, are involved in the GmCDL1 function after the perception of SCN. taken together, this study not only discovers a complete early immune pathway that responds to SCN infection in soybean, but also reveals a molecular mechanism by which plants maintain the activation of the MAPK cascade and resistance.

The MYB Transcription Factor GmMYB78 Negatively Regulates Phytophthora sojae Resistance in Soybean.

Phytophthora root rot is a devastating disease of soybean caused by Phytophthora sojae. However, the resistance mechanism is not yet clear. Our previous studies have shown that GmAP2 enhances sensitivity to P. sojae in soybean, and GmMYB78 is downregulated in the transcriptome analysis of GmAP2-overexpressing transgenic hairy roots. Here, GmMYB78 was significantly induced by P. sojae in susceptible soybean, and the overexpressing of GmMYB78 enhanced sensitivity to the pathogen, while silencing GmMYB78 enhances resistance to P. sojae, indicating that GmMYB78 is a negative regulator of P. sojae. Moreover, the jasmonic acid (JA) content and JA synthesis gene GmAOS1 was highly upregulated in GmMYB78-silencing roots and highly downregulated in overexpressing ones, suggesting that GmMYB78 could respond to P. sojae through the JA signaling pathway. Furthermore, the expression of several pathogenesis-related genes was significantly lower in GmMYB78-overexpressing roots and higher in GmMYB78-silencing ones. Additionally, we screened and identified the upstream regulator GmbHLH122 and downstream target gene GmbZIP25 of GmMYB78. GmbHLH122 was highly induced by P. sojae and could inhibit GmMYB78 expression in resistant soybean, and GmMYB78 was highly expressed to activate downstream target gene GmbZIP25 transcription in susceptible soybean. In conclusion, our data reveal that GmMYB78 triggers soybean sensitivity to P. sojae by inhibiting the JA signaling pathway and the expression of pathogenesis-related genes or through the effects of the GmbHLH122-GmMYB78-GmbZIP25 cascade pathway.

Synthesis, Plant Growth Regulatory Activity, and Transcriptome Analysis of Novel Opabactin Analogs.

Abscisic acid (ABA), a phytohormone, and its analogs have been found to enhance plant resistance to various biotic and abiotic stresses, particularly drought, by activating the ABA signaling pathway. This study used a combination of structure-directed design and molecular docking screening methods to synthesize a novel series of opabactin (OP) analogs. Among them, compounds 4a-4d and 5a showed comparable or superior activity to OP in bioassays, including seed germination and seedling growth inhibition in A. thaliana and rice, stomatal closure, and drought resistance in wheat and soybean. Further transcriptome analysis revealed distinct mechanisms of action between compound 4c and iso-PhABA in enhancing drought tolerance in A. thaliana. These findings highlight the application prospect of 4c and its analogs in agricultural cultivation, particularly in drought resistance. Additionally, they provide new insights into the mechanisms by which different ABA receptor agonists enhance drought resistance.

An enzyme-free and ratiometric biosensor for single nucleotide polymorphism with portable electrochemical system

Portable, low-cost and efficient biosensing systems are valuable for single nucleotide polymorphisms (SNPs) analysis, particularly in resource-limited fields. Herein, a rapid, enzyme-free and ratiometric SNPs biosensor with portable electrochemical system enabling simultaneous recognition and signal amplification is proposed. To demonstrate its versatility and effectiveness, we have selected the human cancer-related KRAS gene and the soybean mosaic virus resistance Rsv3 gene as our analysis models. Our biosensor is constructed based on a combination of strand displacement reactions and hybridization chain reactions (HCR). This unique design enables to differentiate between mutant (MT) and wild (WD) sequences based on the differential release of HCR products on the electrode surfaces. Importantly, this enzyme-free SNPs biosensor concurrently achieves both SNPs recognition and signal amplification, significantly reducing the reaction time to just 40 minutes. Furthermore, we have developed a miniaturized biosensor system that incorporates screen printed gold electrodes (SPGE) and smartphones. This system is integrated with a ratiometric strategy with an limit of detection as low as 1.2 fM, enhancing accuracy and eliminating external interference. This simple SNPs biosensing system possesses high reliability, positioning it as a versatile biosensor for the determination of various SNPs mutations.

Genome-wide association study and haplotype analysis reveal novel candidate genes for resistance to powdery mildew in soybean.

Powdery mildew disease (PMD) is caused by the obligate biotrophic fungus Microsphaera diffusa Cooke & Peck (M. diffusa) and results in significant yield losses in soybean (Glycine max (L.) Merr.) crops. By identifying disease-resistant genes and breeding soybean accessions with enhanced resistance, we can effectively mitigate the detrimental impact of PMD on soybeans. We analyzed PMD resistance in a diversity panel of 315 soybean accessions in two locations over 3 years, and candidate genes associated with PMD resistance were identified through genome-wide association studies (GWAS), haplotype analysis, qRT-PCR, and EMS mutant analysis. Based on the GWAS approach, we identified a region on chromosome 16 (Chr16) in which 21 genes form a gene cluster that is highly correlated with PMD resistance. In order to validate and refine these findings, we conducted haplotype analysis of 21 candidate genes and indicated there are single nucleotide polymorphisms (SNPs) and insertion-deletions (InDels) variations of Glyma.16G214000, Glyma.16G214200, Glyma.16G215100 and Glyma.16G215300 within the coding and promoter regions that exhibit a strong association with resistance against PMD. Subsequent structural analysis of candidate genes within this cluster revealed that in 315 accessions, the majority of accessions exhibited resistance to PMD when Glyma.16G214300, Glyma.16G214800 and Glyma.16G215000 were complete; however, they demonstrated susceptibility to PMD when these genes were incomplete. Quantitative real-time PCR assays (qRT-PCR) of possible candidate genes showed that 14 candidate genes (Glyma.16G213700, Glyma.16G213800, Glyma.16G213900, Glyma.16G214000, Glyma.16G214200, Glyma.16G214300, Glyma.16G214500, Glyma.16G214585, Glyma.16G214669, Glyma.16G214700, Glyma.16G214800, Glyma.16G215000, Glyma.16G215100 and Glyma.16G215300) were involved in PMD resistance. Finally, we evaluated the PMD resistance of mutant lines from the Williams 82 EMS mutations library, which revealed that mutants of Glyma.16G214000, Glyma.16G214200, Glyma.16G214300, Glyma.16G214800, Glyma.16G215000, Glyma.16G215100 and Glyma.16G215300, exhibited sensitivity to PMD. Combined with the analysis results of GWAS, haplotypes, qRT-PCR and mutants, the genes Glyma.16G214000, Glyma.16G214200, Glyma.16G214300, Glyma.16G214800, Glyma.16G215000, Glyma.16G215100 and Glyma.16G215300 were identified as highly correlated with PMD resistance. The candidate genes identified above are all NLR family genes, and these discoveries deepen our understanding of the molecular basis of PMD resistance in soybeans and will be useful for guiding breeding strategies.

Identification and Genetic Dissection of Resistance to Red Crown Rot Disease in a Diverse Soybean Germplasm Population.

Red crown rot (RCR) disease caused by Calonectria ilicicola negatively impacts soybean yield and quality. Unfortunately, the knowledge of the genetic architecture of RCR resistance in soybeans is limited. In this study, 299 diverse soybean accessions were used to explore their genetic diversity and resistance to RCR, and to mine for candidate genes via emergence rate (ER), survival rate (SR), and disease severity (DS) by a multi-locus random-SNP-effect mixed linear model of GWAS. All accessions had brown necrotic lesions on the primary root, with five genotypes identified as resistant. Nine single-nucleotide polymorphism (SNP) markers were detected to underlie RCR response (ER, SR, and DS). Two SNPs colocalized with at least two traits to form a haplotype block which possessed nine genes. Based on their annotation and the qRT-PCR, three genes, namely Glyma.08G074600, Glyma.08G074700, and Glyma.12G043600, are suggested to modulate soybean resistance to RCR. The findings from this study could serve as the foundation for breeding RCR-tolerant soybean varieties, and the candidate genes could be validated to deepen our understanding of soybean response to RCR.

Natural variation of GmFNSII-2 contributes to drought resistance by modulating enzyme activity in soybean

As an essential crop that provides vegetable oil and protein, soybean (Glycine max (L.) Merr.) is widely planted all over the world. However, the scarcity of water resources worldwide has seriously impacted on the quality and yield of soybean. To address this, exploring excellent genes for improving drought resistance in soybean is crucial. In this study, we identified natural variations of GmFNSII-2 (flavone synthase II) significantly affect the drought resistance of soybeans. Through sequence analysis of GmFNSII-2 in 632 cultivated and 44 wild soybeans nine haplotypes were identified. The full-length allele GmFNSII-2C, but not the truncated allele GmFNSII-2A possessing a nonsense nucleotide variation, increased enzyme activity. Further research found that GmDREB3, known to increase soybean drought resistance, bound to the promoter region of GmFNSII-2C. GmDREB3 positively regulated the expression of GmFNSII-2C, increased flavone synthase abundance and improved the drought resistance. Furthermore, a single-base mutation in the GmFNSII-2C promoter generated an additional drought response element (CCCCT), which had stronger interaction strength with GmDREB3 and increased its transcriptional activity under drought conditions. The frequency of drought-resistant soybean varieties with Hap 1 (Pro:GmFNSII-2C) has increased, suggesting that this haplotype may be selected during soybean breeding. In summary, GmFNSII-2C could be used for molecular breeding of drought-tolerant soybean.