HG Type Research Articles

Effective identification of soybean candidate genes involved in resistance to soybean cyst nematode via direct whole genome re-sequencing of two segregating mutants.

Three soybean candidate genes involved in resistance to soybean cyst nematode race 4 were identified via direct whole genome re-sequencing of two segregating mutants. The genes conferring resistance to soybean cyst nematode (SCN) race 4 (Hg type 1.2.3.5.7) in soybean (Glycine max L. Merr.) remains unknown. Next generation sequencing-based methods identify a wide range of targets, it is difficult to identify genes underlying traits. Use of the MutMap and QTL-seq methods to identify trait candidate genes needs backcrossing and is very time-consuming. Here we report a simple method to effectively identify candidate genes involved in resistance to SCN race 4. Two ethane methylsulfonate mutagenized mutants of soybean 'PI 437654', whose SCN race 4-infection phenotype altered, were selected. Six relevant whole genomes were re-sequenced, and then calling of genomic variants (SNPs and InDels) was conducted and compared to 'Williams 82'. The comparison eliminated many genomic variants from the mutant lines that overlapped two non-phenotypic but mutant progeny plants, wild-type PI 437654 and 'Zhonghuang 13'. Finally, only 27 mutations were found among 10 genes. Of these 10 genes, 3 genes, Glyma.09g054000, Glyma.16g065700 and Glyma.18g192200 were overlapped between two phenotypic mutant progeny plants. Therefore, the three genes may be the candidate genes involved in resistance of PI 437654 to soybean cyst nematode race 4. This method simplifies the effective identification of candidate genes.

Registration of ‘S11‐20124C’ Soybean with High Yield Potential, Multiple Nematode Resistance, and Salt Tolerance

‘S11‐20124C’ (Reg. No. CV‐532, PI 689118) is a high‐yielding semi‐determinate early maturity group V (5.1) conventional soybean [Glycine max (L.) Merr.] cultivar developed and released in 2017 by the University of Missouri–Fisher Delta Research Center Soybean Breeding program. It was developed through conventional breeding from a cross between ‘S05‐11482’ × ‘S06‐4649RR’. The development of high‐yielding conventional soybean became advantageous due to premium prices offered for non–genetically modified soybean products, as well as lower seed costs compared with herbicide‐tolerant cultivars. Additionally, early maturity group V (5.1) soybeans are highly desirable for early planting and after wheat (Triticum aestivum L.) in double cropping systems. S11‐20124C was evaluated in 113 environments from 2012 to 2016 in Missouri and other southern states. It is demonstrated to be well adapted through its consistent superior or equivalent performance to the commercial checks with similar maturity. S11‐20124C has a wide disease resistance package, including moderate resistance to soybean cyst nematode races 1, 2, 3, 5, and 14 (HG Type 2.5.7, Type 1.2.5.7, Type 7, Type 2.5.7, Type 1.3.6.7 respectively) and resistance to southern root‐knot nematode and reniform nematode . Seed averages 416 g kg−1 protein and 245 g kg−1 oil. High yield potential, resistance to multiple diseases, and broad adaptation make S11‐20124C a good choice for soybean growers across US southern states.

Genome wide association study discovers genomic regions involved in resistance to soybean cyst nematode (Heterodera glycines) in common bean.

Common bean (Phaseolus vulgaris L.) is an important high protein crop grown worldwide. North Dakota and Minnesota are the largest producers of common beans in the USA, but crop production is threatened by soybean cyst nematode (SCN; Heterodera glycines Ichinohe) because most current cultivars are susceptible. Greenhouse screening data using SCN HG type 0 from 317 plant introductions (PI’s) from the USDA core collection was used to conduct a genome wide association study (GWAS). These lines were divided into two subpopulations based on principal component analysis (Middle American vs. Andean). Phenotypic results based on the female index showed that accessions could be classified as highly resistant (21% and 27%), moderately resistant (51% and 48%), moderately susceptible (27% and 22%) and highly susceptible (1% and 3%) for Middle American and Andean gene pools, respectively. Mixed models with two principal components (PCs) and kinship matrix for Middle American genotypes and Andean genotypes were used in the GWAS analysis using 3,985 and 4,811 single nucleotide polymorphic (SNP) markers, respectively which were evenly distributed across all 11 chromosomes. Significant peaks on Pv07, and Pv11 in Middle American and on Pv07, Pv08, Pv09 and Pv11 in Andean group were found to be associated with SCN resistance. Homologs of soybean rhg1, a locus which confers resistance to SCN in soybean, were identified on chromosomes Pv01 and Pv08 in the Middle American and Andean gene pools, respectively. These genomic regions may be the key to develop SCN-resistant common bean cultivars.

Registration of ‘TN09‐008’ Soybean Cyst Nematode–Resistant Cultivar

The conventional soybean [Glycine max (L.) Merr.] line ‘TN09‐008’ (Reg. No. CV‐527, PI 686907) was released by University of Tennessee Agricultural Research in 2017 as a cultivar on the basis of its high seed yield potential in Tennessee and the southern region of the United States. TN09‐008 is resistant to HG types 1.2.5.7, 5.7, and 2.5.7 (races 2, 3, and 5, respectively) of soybean cyst nematode (SCN), resistant to stem canker, and shows field tolerance to sudden death syndrome and frogeye leaf spot. TN09‐008 is a maturity group V line with relative maturity of approximately 5.3. It will serve as an excellent parent line in breeding for broad resistance to SCN and several other important pathogens of soybean.

Cuticular wax variants in a population of switchgrass (Panicum virgatum L.)

Leaf cuticular waxes are known to influence both biotic and abiotic stress tolerances of plants. The objective of this work was to characterize the wax phenotypic diversity present in a population of 1849 switchgrass plants. We identified 92 visually distinct variant plants that possessed altered leaf glaucousness relative to the common standard type (ST), which exhibited a bluish-white (glaucous) leaf color. The variants could be grouped into three classes: 1) non-glaucous types (NG) that possessed a shiny green leaf surface, 2) reduced glaucous types (RG) that appeared less glaucous than ST, and 3) highly glaucous types (HG) that exhibited more intense bluish-white color than ST. Analyses of total cuticular wax content averaged over each of three NG (mean 304.79 ± 15.16 μg/dm2), RG (mean 533.33 ± 21.62 μg/dm2) and HG types (mean 1228.23 ± 45.74 μg/dm2) showed significant differences (P < 0.001) from three selected STs (mean 810.92 ± 30.57 μg/dm2). Analysis of wax composition among these selected types revealed that the C33 β-diketones were the most abundant wax compounds in all but NG types. Field emission scanning electron microscopy showed that abaxial leaf surfaces exhibited predominantly rod-shaped crystals, and adaxial surfaces exhibited predominantly plate-shaped wax crystals on all lines, except for NG that lacked wax crystals on the abaxial leaf surface. As a target for crop improvement, this study reveals that a large amount of variation for cuticle waxes exists within this switchgrass germplasm.

Identification of HG Types of Soybean Cyst Nematode Heterodera glycines and Resistance Screening on Soybean Genotypes in Northeast China.

Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is a serious soybean pathogen worldwide. HG Type 0 had been a predominant SCN in Heilongjiang province, the largest soybean (Glycine max L.) producing region in China. Recently, increased virulence on resistant cultivars originally developed for resistance to HG Type 0 was observed in fields. In order to identify new cultivars resistant to local SCN populations, two soil samples were collected from two counties (Anda and Wuchang) in which increased virulence on resistant cultivars occurred, and single-cyst cultures from each soil sample were maintained for more than five generations. Two single-cyst cultures from the Anda sample were identified as HG Type 1.2.3.5.6.7 and HG Type 1.3, and one single-cyst culture from Wuchang was identified as HG Type 2.5.7. Then 18 soybean genotypes, including 11 local cultivars originally developed for resistance to HG Type 0, were used to evaluate resistance response to the three identified SCN populations. Various levels of resistance or susceptibility to the three SCN populations were observed among 18 genotypes. Two tests produced similar results for the three SCN populations. Both 'Kangxian12' and 'Kangxian13' showed resistance or moderate resistance to HG Type 2.5.7, HG Type 1.2.3.5.6.7 and HG Type 1.3. The germplasm '09-138' was resistant to HG Type 1.3 and HG Type 1.2.3.5.6.7. Cultivars with 'Peking'-resistance were resistant or moderately resistant to HG Type 2.5.7 in both tests except for 'Kangxian8' in test 1. The identified resistant varieties would be valuable sources of breeding materials for resistance against multiple SCN populations.

Genetically Diverse Soybean Cyst Nematode–Resistant Full‐Sib Soybean Germplasm Lines AR4SCN, AR5SCN, AR6SCN, AR7SCN, and AR8SCN

Soybean [Glycine max (L.) Merr.] yields will be protected by introgressing pathogen resistance, an objective of soybean breeding for pathogen resistance at Iowa State University (ISU). Germplasms AR4SCN (Reg. No. GP‐410, PI 684651), AR5SCN (Reg. No. GP‐411, PI 684652), AR6SCN (Reg. No. GP‐412, PI 684653), AR7SCN (Reg. No. GP‐413, PI 684654), and AR8SCN (Reg. No. GP‐414, PI 684655), are resistant to soybean cyst nematode (SCN, Heterodera glycines [HG] Ichinohe) HG type 0 (Race 3) and HG type 1.3.6.7 (Race 14). In 2007, ISU Projects 3722 of the Agronomy Department and Project 3384 of the Plant Pathology Department, the Iowa Agricultural and Home Economics Experiment Station, and the ISU Research Foundation released the lines. Each line is an F12:13 bulk of 60 agronomically uniform plants from the cross of the genetically diverse SCN parents PI 88788 and ‘Columbia’. The cross made at the Isabela Substation, Puerto Rico, underwent generation advances in Puerto Rico and Iowa. Phenotyping/molecular characterizations of lines at Arelli's, Cianzio's and Diers’ labs confirmed the presence of high copy numbers of the full‐length sequence repeat of the highly important major PI 88788‐type rhg1‐b gene, conferring high levels of SCN resistance on each germplasm. In Iowa, average seed yield of the maturity group (MG) II line AR4SCN was 57% of the check ‘Dwight’. For MG III lines (AR5SCN, AR6SCN, AR7SCN, AR8SCN), yield was 77% of ‘Macon’. The germplasms will serve in the development of SCN‐resistant genotypes adapted to northern US regions where SCN HG type 0 and/or 1.3.6.7 may be prevalent. Lines may also serve as research genetic stocks.

Effect of Soybean Cyst Nematode Resistance Source and Seed Treatment on Population Densities of Heterodera glycines, Sudden Death Syndrome, and Yield of Soybean.

A three-year study was conducted in Illinois, Indiana, Iowa, Michigan, and Ontario, Canada, from 2013 through 2015 to determine the effect of soybean (Glycine max) cultivars' source of soybean cyst nematode (SCN; Heterodera glycines) resistance on SCN population densities, sudden death syndrome (SDS; caused by Fusarium virguliforme), and yield of soybean. Five cultivars were evaluated with and without fluopyram seed treatment at each location. Cultivars with no SCN resistance had greater SDS severity, greater postharvest SCN egg counts (Pf), and lower yield than cultivars with plant introduction (PI) 548402 (Peking) and PI 88788-type of SCN resistance (P < 0.05). Cultivars with Peking-type resistance had lower Pf than those with PI 888788-type and no SCN resistance. In two locations with HG type 1.2-, cultivars with Peking-type resistance had greater foliar disease index (FDX) than cultivars with PI 88788-type. Fluopyram seed treatment reduced SDS and improved yield compared with a base seed treatment but did not affect SCN reproduction and Pf (P > 0.05). FDX and Pf were positively correlated in all three years (P < 0.01). Our results indicate that SDS severity may be influenced by SCN population density and HG type, which are important to consider when selecting cultivars for SCN management.

Systematic Mutagenesis of Serine Hydroxymethyltransferase Reveals an Essential Role in Nematode Resistance.

Rhg4 is a major genetic locus that contributes to soybean cyst nematode (SCN) resistance in the Peking-type resistance of soybean (Glycine max), which also requires the rhg1 gene. By map-based cloning and functional genomic approaches, we previously showed that the Rhg4 gene encodes a predicted cytosolic serine hydroxymethyltransferase (GmSHMT08); however, the novel gain of function of GmSHMT08 in SCN resistance remains to be characterized. Using a forward genetic screen, we identified an allelic series of GmSHMT08 mutants that shed new light on the mechanistic aspects of GmSHMT08-mediated resistance. The new mutants provide compelling genetic evidence that Peking-type rhg1 resistance in cv Forrest is fully dependent on the GmSHMT08 gene and demonstrates that this resistance is mechanistically different from the PI 88788-type of resistance that only requires rhg1 We also demonstrated that rhg1-a from cv Forrest, although required, does not exert selection pressure on the nematode to shift from HG type 7, which further validates the bigenic nature of this resistance. Mapping of the identified mutations onto the SHMT structural model uncovered key residues for structural stability, ligand binding, enzyme activity, and protein interactions, suggesting that GmSHMT08 has additional functions aside from its main enzymatic role in SCN resistance. Lastly, we demonstrate the functionality of the GmSHMT08 SCN resistance gene in a transgenic soybean plant.

Genome-wide identification of soybean microRNA responsive to soybean cyst nematodes infection by deep sequencing

BackgroundThe soybean cyst nematode (SCN), Heterodera glycines, is one of the most devastating diseases limiting soybean production worldwide. It is known that small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), play important roles in regulating plant growth and development, defense against pathogens, and responses to environmental changes.ResultsIn order to understand the role of soybean miRNAs during SCN infection, we analyzed 24 small RNA libraries including three biological replicates from two soybean cultivars (SCN susceptible KS4607, and SCN HG Type 7 resistant KS4313N) that were grown under SCN-infested and -noninfested soil at two different time points (SCN feeding establishment and egg production). In total, 537 known and 70 putative novel miRNAs in soybean were identified from a total of 0.3 billion reads (average about 13.5 million reads for each sample) with the programs of Bowtie and miRDeep2 mapper. Differential expression analyses were carried out using edgeR to identify miRNAs involved in the soybean-SCN interaction. Comparative analysis of miRNA profiling indicated a total of 60 miRNAs belonging to 25 families that might be specifically related to cultivar responses to SCN. Quantitative RT-PCR validated similar miRNA interaction patterns as sequencing results.ConclusionThese findings suggest that miRNAs are likely to play key roles in soybean response to SCN. The present work could provide a framework for miRNA functional identification and the development of novel approaches for improving soybean SCN resistance in future studies.

Registration of ‘Agustina’ Soybean Cultivar

‘Agustina’ soybean [Glycine max (L.) Merr.] cultivar (Reg. No. CV‐524, PI 679941) was developed by the Clemson Pee Dee Research and Extension Center in Florence, SC. It was released in 2016 because of its ability to delay flowering under short‐day conditions and produce high yields, which is due in part to the long juvenile (LJ) trait. The LJ trait extends the period between germination and flowering under short‐day growing conditions. Thus, the latitude in which the cultivar is grown can have a large impact on maturity. When grown in Florence, SC, Agustina was tested as a maturity group (MG) VIII, high‐yielding, conventional (non‐genetically modified) cultivar. When tested ∼12° further south in Tampico, Mexico, Agustina was classified as a MG IX cultivar. In Tampico, (27° N), the furthest south it was tested, Agustina was the highest‐yielding line in the test, outyielding the highest‐yielding check by 222 kg ha−1. Agustina traces to a single plant selection in the F5 generation in 2010 from a cross between SC98‐1850 and ‘Manokin.’ Agustina exhibits white flowers, tawny pubescence, and an imperfect black hilum color. It has excellent resistance to soybean cyst nematode HG type 2.5.7 (race 1) and HG type 0 (race 3) and moderate resistance to HG type 2.5.7(race 5). Agustina is a highly versatile cultivar that performs well across multiple environments.

Quantitative trait loci with additive and epistatic effects underlying resistance to two HG types of soybean cyst nematode

AbstractThe resistance of soybean (Glycine max L. Merr.) cultivars varies with the different races of the soybean cyst nematode (SCN), Heterodera glycines, referred to as HG types (biotypes). Resistant cultivars with durable resistance are emphasized in recent years. The aim here was to identify quantitative trait loci (QTLs) for resistance to two SCN HG types (HG type 2.5.7, race 1; and HG type 1.2.3.5.7, race 4) in resistant cultivar ‘L‐10’ and to analyse the additive and epistatic effects of the identified QTLs. A total of 140 F5‐derived F10 recombinant inbred lines (F5:10 RILs) were advanced via single‐seed‐descent from the cross between ‘L‐10’ (broadly resistant to SCN) and “Heinong 37” (SCN‐susceptible). For SCN HG type 2.5.7 and HG type 1.2.3.5.7 resistance, three and six QTLs for resistance to SCN HG type 2.5.7 and HG type 1.2.3.5.7 were identified, respectively, most of which could explain &lt;10% of the phenotypic variation. Among these QTLs, five were identified over 2 years, while the other QTLs were detected in either 2009 or 2010. QSCN1‐2, located near the SSR marker Sat_069 of linkage group D1b (Chromosome, 2), was responsible for the largest proportion of phenotypic variation (16.01% in 2009 and 18.94% in 2010), suggested that it could effectively be used as a candidate QTL for the marker‐assisted selection (MAS) of soybean lines resistant to SCN. Additionally, for SCN HG type 2.5.7 and HG type 1.2.3.5.7 resistance, two and four QTLs showed an additive effect (a), respectively. One epistatic pair of QTLs (QSCN1‐1‐QSCN1‐3) for SCN HG type 2.5.7 resistance and eight epistatic pairs of QTLs for SCN HG type 1.2.3.5.7 resistance were found to have significant aa effects, among which one pair of QTLs (QSCN4‐4 and QSCN4‐5) contributed a large proportion of aa effects (3%). The results indicated that additive and epistatic effects could significantly affect SCN resistance. Therefore, both of a and aa effects should be considered in MAS programmes.

Resistance to Soybean Cyst Nematode: Rhg1

The genes underlying rhg1 lie at a sometimes dominant sometimes co-dominant locus, necessary for resistance to all Hg types of the soybean (Glycine max (L.) Merr.) cyst nematode (Heterodera glycines). Genomic research identified; nucleotide changes within a candidate gene encoding a receptor like kinase (RLK) that were capable of altering root development and thereby part of the resistance to Hg types 0 (race 3); changes in a laccase that are capable of altering cyst development; and genes underlying changes in membrane biology. This set of three genes are subject to co-selection with a modifier locus on another linkage block. Root development is slowed in the resistant seedling and results in end of season yield loss when SCN is not present. However, in the presence of SCN resistant seedling roots grow just as vigorously as the now slower growing parasitized susceptible roots and therefore show little loss to SCN parasitism. In some genotypes but not others the RLK can act alone to confer resistance. Functional paralogs of the three gene cluster have been found on other linkage groups including A1, B1, G, and O and these can be functional in different sources of resistance like G. soja, PI 437654 and PI438489B. At rhg1 the allele differences change the structure, interacting partners and activity of the LRR protein and the laccase. The changes between the alleles result in about 30 other proteins (judged by 2 Dgels), 112 metabolites (by FTICRMS) and 8 metabolites (by GCMS) to increase in abundance in roots during SCN infection in the resistant NILs. Understanding the basis of root stunting by resistance alleles will be used to improve methods for developing new nematode resistant soybean cultivars that do not suffer from the yield suppression and low seed germination rates of existing cultivars.

Loci and candidate genes conferring resistance to soybean cyst nematode HG type 2.5.7

BackgroundSoybean (Glycine max L. Merr.) cyst nematode (SCN, Heterodera glycines I,) is a major pest of soybean worldwide. The most effective strategy to control this pest involves the use of resistant cultivars. The aim of the present study was to investigate the genome-wide genetic architecture of resistance to SCN HG Type 2.5.7 (race 1) in landrace and elite cultivated soybeans.ResultsA total of 200 diverse soybean accessions were screened for resistance to SCN HG Type 2.5.7 and genotyped through sequencing using the Specific Locus Amplified Fragment Sequencing (SLAF-seq) approach with a 6.14-fold average sequencing depth. A total of 33,194 SNPs were identified with minor allele frequencies (MAF) over 4%, covering 97% of all the genotypes. Genome-wide association mapping (GWAS) revealed thirteen SNPs associated with resistance to SCN HG Type 2.5.7. These SNPs were distributed on five chromosomes (Chr), including Chr7, 8, 14, 15 and 18. Four SNPs were novel resistance loci and nine SNPs were located near known QTL. A total of 30 genes were identified as candidate genes underlying SCN resistance.ConclusionsA total of sixteen novel soybean accessions were identified with significant resistance to HG Type 2.5.7. The beneficial alleles and candidate genes identified by GWAS might be valuable for improving marker-assisted breeding efficiency and exploring the molecular mechanisms underlying SCN resistance.

Quantitative Trait Loci (QTL) that Underlie SCN Resistance in Soybean [Glycine max (L.) Merr.] PI438489B by ‘Hamilton’ Recombinant Inbred Line (RIL) Population

Soybean cyst nematode caused by Heterodera glycines Ichinohe is the most devastating pest in soybean [Glycine max (L.) Merr.]. Resistance to SCN is complex, polygenic, race and cultivar specific, and it is controlled by several quantitative trait loci (QTL). Our objective was to identify and map QTL for SCN resistance to races 3 (HG Type 0) and 5 (HG Type 2.5.7) using a high density SNP-based genetic linkage map based on the PI438489B by ‘Hamilton’ (PIxH, n=50) recombinant inbred line population. The PI438489B by Hamilton map contained 648 SNPs distributed on 31 LGs with coverage of 1,524.7 cM and an average distance of 2.35 cM between two markers (Kassem et al., 2011). Using interval mapping (IM) and composite interval mapping (CIM), eight QTL were identified for SCN resistance to races 3 and 5 on 7 different soybean chromosomes. Four QTL for resistance to SCN race 3 were identified and mapped on chromosomes 7, 13, 15, and 16. Similarly, four QTL for resistance to SCN race 5 were identified and mapped on chromosomes 5, 8, and 11. The QTL identified here will be highly beneficial in breeding programs to develop cultivars with resistance to both SCN races 3 and 5.

Genome-wide association study for soybean cyst nematode resistance in Chinese elite soybean cultivars

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is a highly recalcitrant endoparasite of soybean roots, causing more yield loss than any other pest. To identify quantitative trait loci (QTL) controlling resistance to SCN (HG type 2.5.7, race 1), a genome-wide association study (GWAS) was performed. The association panel, consisting of 120 Chinese soybean cultivars, was genotyped with 7189 single nucleotide polymorphism (SNPs). A total of 6204 SNPs with minor allele frequency >0.05 were used to estimate linkage disequilibrium (LD) and population structure. The mean level of LD measured by r 2 declined very rapidly to half its maximum value (0.51) at 220 kb. The overall population structure was approximately coincident with geographic origin. The GWAS results identified 13 SNPs in 7 different genomic regions significantly associated with SCN resistance. Of these, three SNPs were localized in previously mapped QTL intervals, including rhg1 and Rhg4. The GWAS results also detected 10 SNPs in 5 different genomic regions associated with SCN resistance. The identified loci explained an average of 95.5% of the phenotypic variance. The proportion of phenotypic variance was due to additive genetic variance of the validated SNPs. The present study identified multiple new loci and refined chromosomal regions of known loci associated with SCN resistance. The loci and trait-associated SNPs identified in this study can be used for developing soybean cultivars with durable resistance against SCN.

Accessions of Perennial Glycine Species With Resistance to Multiple Types of Soybean Cyst Nematode (Heterodera glycines).

Soybean cyst nematode (SCN; Heterodera glycines; HG) is a widely occurring and damaging pathogen that limits soybean production. Developing resistant cultivars is the most cost-effective method for managing this disease. Genes conferring SCN resistance in soybean have been identified; however, there are SCN populations that overcome known resistance genes. In order to identify additional sources of resistance and potentially new resistance genes, 223 plant introductions (PIs) of G. tomentella and 59 PIs of 12 other perennial Glycine species were inoculated with HG Types 0, HG 2, and HG 1.2.3, and then 36 PIs out of this set were further evaluated with HG Type 1.2.3.4.5.6.7, a population that overcomes all the resistance genes in soybean. Of 223 G. tomentella PIs evaluated, 86 were classified as resistant to three HG types, 69 as resistant to two HG types, and 22 as resistant to one HG type. Of the other 12 perennial Glycine species, all PIs of G. argyrea and G. pescadrensis were resistant to all three HG types. Of the 36 PIs challenged with HG Type 1.2.3.4.5.6.7, 35 were resistant with 16 showing no cyst reproduction. Our study confirms that there are high levels of resistance to SCN among the perennial Glycine species. This represents an untapped resource for use in genetic studies and for improving resistance to SCN in soybean.

Ethnic variations in mercury exposure from seafood consumption and the risk of Kawasaki disease in young children

Kawasaki disease (KD) is an acute febrile illness predominately affecting children &lt;5 years that can result in serious cardiovascular complications such as coronary artery lesion formation. The cause of KD remains unknown 50 years after Kawasaki first described the illness in Japan, while KD has since replaced rheumatic fever as the leading cause of acquired heart disease for children in the developed world. KD has become the most commonly diagnosed pediatric vasculitis with the highest incidence rates of KD reported from East Asian countries such as Japan, Korea, and Taiwan. Even when residing in Western nations, East Asian children still have 10 to 20 times the risk of developing KD than children of other ethnicities. Speculation that genetic differences between ethnic groups account for the ethnic disparity in KD rates led to the discovery and confirmation of numerous susceptibility loci, although these risk alleles only appear to confer risk passively to the currently unknown environmental triggers of KD. Previously, we described how ITPKC susceptibility in KD patients would render these individuals vulnerable to mercury (Hg)‐induced autoimmunity through the induction of intracellular calcium release with downstream effects upon cell signaling, immune proliferation, and gene expression via the Ca2+/NFAT pathway. This led us to hypothesize that the ethnic disparities in KD risk may be accounted for by variations in Hg exposure rates, particularly from significant differences in total methylmercury (MeHg) intake from seafood. We examined two separate cohorts that were nationally representative of either KD hospitalization rates or toxic metal concentrations in the blood in our initial investigations. Our results demonstrated that increasing ethnic KD risk between Caucasian, Hispanic, Black, and Asian children was significantly associated with average blood levels and detection rates of Hg or cadmium (Cd) but not lead (Pb), manganese (Mn), or selenium (Se). In our most recent investigations using the same two datasets, we observed that ethnic KD risk was significantly associated with increasing consumption of total fish and seafood but not shellfish. Further examinations by Hg type demonstrated that MeHg from seafood is the primary source of blood Hg in children, while average blood MeHg levels but not inorganic or ethylmercury were significantly associated with increasing ethnic KD risk. Lastly, ethnic KD risk was significantly associated with molar ratios of Hg and Se in the blood that are indicative of seafood consumption. We conclude that Hg exposure particularly from seafood consumption may increase susceptibility for the development of KD in young children or trigger the disease, itself. However, our hypothesis requires determinations of blood Hg levels and cumulative Hg exposure such as from dietary seafood intake in KD patients, which are currently lacking and that we are presently examining.Support or Funding InformationNone

Identification of Loci Underlying Seed Yield in Recombinant Inbred and Near Isogeneic Soybean Lines Derived from Flyer by Hartwig

Two major determinants of soybean [Glycine max (L.) Merr.] seed yield were resistances to the soybean cyst nematode (SCN) and sudden death syndrome (SDS). Two loci were identified rhg1/Rfs2 and rhg3/rfs5 (for resistance to SCN, Heterodera glycines (I.) HG Type 1.3- (race 14), HG Type 0 (race 3) and SDS caused by Fusarium virguliforme (Roy & Rupe)). The aim of this study was to identify quantitative trait loci (QTL) underlying seed yield. Used were 142 microsatellite markers and the recombinant inbred line population (RIL) ‘Flyer’ × ‘Hartwig’ (F × H; n=92). Flyer (F) was high yielding but SCN and SDS susceptible. Hartwig (H) was lower yielding but resistant to all SCN Hg Types and SDS. Four regions on 3 chromosomes were associated with seed yield. The first region on chromosome 9 (Gm9, qYld09.1), identified by the microsatellite marker Satt539-Satt242 (LOD 2.9, 13% variation) derived the beneficial allele from Hartwig (F allele 2.76 ± 0.06 Mg/Ha; H allele 2.98 ± 0.03 Mg/ha). The second region on Gm9 (qYld09.2) between Satt337 and Satt326 spanned 1.4 cM (LOD of 5.31, 20.2% variation) and the beneficial allele derived from Flyer (0.22 Mg/ha F allele 2.98 ± 0.03, H allele 2.77 ± 0.04 Mg/Ha). The third and fourth QTL were identified in genetic linkage groups D2 (qYld19.1) and G (qYld18.1) in regions previously associated with resistance to SCN. The region encompassing rhg1/Rfs2 on Gm18 between the microsatellite marker TMD1 and Satt610 spanned 15.5 cM (LOD 3.05, 15.8 % variation, F allele 2.37 ± 0.035; H allele 2.91 ± 0.058 Mg/Ha). The region on linkage group D2 between Satt514 and Satt488 spanned 32.6 cM (LOD 2.57, Kas13.3% variation, F allele 2.79 ± 0.049; H allele 3.1 ± 0.043 Mg/Ha). The QTL detected will allow marker assisted selection to stack seed yield, with pest resistance traits (rhg1/Rfs2/qYld18.1; H/H/H allele) and recombinant loci (Rhg5/Rfs2/qYld19.1; H/F/H alleles).

Increase in Soybean Cyst Nematode Virulence and Reproduction on Resistant Soybean Varieties in Iowa From 2001 to 2015 and the Effects on Soybean Yields

Management of the soybean cyst nematode (SCN) relies heavily on use of SCN-resistant soybean varieties to limit nematode reproduction and minimize yield loss. For Iowa, almost all SCN-resistant soybean varieties contain SCN resistance genes from a breeding line named Plant Introduction (PI) 88788. Iowa State University conducts experiments to evaluate numerous SCN-resistant and three to four SCN-susceptible soybean varieties in up to nine field experiments across Iowa each year. Data on SCN population density, virulence (SCN race and HG type), soybean yield, precipitation, and growing degree days from more than 25,000 four-row plots in field experiments conducted from 2001 to 2015 were analyzed to determine how these factors affected SCN reproduction and yield. SCN population densities were positively correlated with temperatures and negatively associated with precipitation during the growing seasons, indicating that SCN reproduction was greatest in hot, dry years. Over the years, virulence of SCN populations on PI 88788 increased in the fields in which the experiments were conducted, resulting in increased end-of-season SCN population densities and reduced yields of SCN-resistant soybean varieties with the PI 88788 source of resistance. These results indicate that soybean yield loss caused by SCN on resistant varieties with the common PI 88788 source of resistance likely will increase as virulence of SCN populations increases unless new sources of resistance become widely available and used in the future.