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Two species of potato cyst nematodes (PCNs), Globodera rostochiensis (Woll.) and Globodera pallida (Stone), threaten potato (Solanum tuberosum L.) production worldwide. PCNs are remarkably persistent in soil and can reduce potato yield significantly. The most sustainable approach to PCN control is deploying resistant cultivars. This review focuses on the knowledge needed to conduct a successful PCN resistance breeding program, including identifying resistance sources in wild species, introgressing them into cultivated potato, and sifting through clones to identify a marketable potato. Core Ideas: Potato cyst nematodes (PCNs) are a serious pest worldwide.Breeding resistant potato varieties is the most sustainable way to control these pests.Breeding for resistance to PCNs requires sustained teamwork between a breeder and nematologist. [ABSTRACT FROM AUTHOR]

Soybean sudden death syndrome (SDS) is a disease caused by a soil‐borne fungus, Fusarium virguliforme. Many genetic studies have attempted to identify genes responsible for the quantitative host resistance to SDS. Three recombinant inbred line (RIL) populations were evaluated for foliar SDS resistance at a naturally infested field site in Decatur, MI, during the 2014 and 2015 growing seasons. Lines were evaluated for disease severity (DS) on a 1–9 scale, disease incidence (DI) as an estimate of the percentage of plants with symptoms per plot, and disease index (DX) as a metric which integrates DS and DI. Phenotypic data was spatially adjusted to account for uneven pathogen distribution in the naturally infested field. A subset of RILs from each population were genotyped with the SoySNP6K Illumina Infinium BeadChip. Linkage maps unique to each population were constructed using JoinMap ver. 2. Composite interval mapping was performed using WinQTLCartographer ver. 2.5. Three quantitative trait loci (QTL) were identified across 2 yr and/or multiple populations. One QTL on Chromosome 10 appeared to be colocalized with the E2 maturity locus. Another QTL identified was on Chromosome 18, in a region which has been demonstrated to provide soybean cyst nematode (SCN) and SDS resistance in many studies (rhg1/Rfs2). Core Ideas: The results confirmed the identification of a major host resistance quantitative trait loci on Chromosome Gm18.This quantitative trait loci has also been identified as a region which has resistance to soybean cyst nematode.The results suggest a connection between sudden death syndrome and soybean cyst nematode. [ABSTRACT FROM AUTHOR]

Southern root‐knot nematode (SRKN) is one of the most yield‐suppressing pathogens in soybean [(Glycine max (L.) Merr.] in the United States. With limited chemical and cultural management options, the use of genetic resistance is the most efficient and economical approach to control SRKN. A major quantitative trait locus (QTL) mapped to chromosome 10 is the primary source of resistance in soybean cultivars; however, limited studies have been conducted to evaluate its efficacy in minimizing yield suppression under field conditions with SRKN pressure. This study evaluated the yield performance of 202 elite soybean lines in field conditions with variable distribution of SRKN. Soybean lines were characterized based on the presence of the major QTL on chromosome 10 and grown in four‐row yield plots across six environments over 2 yr. Plots were soil sampled and enumerated to determine nematode population densities. No statistically significant differences in yield performance between resistant and susceptible lines were observed in the absence of nematode pressure, indicating no yield drag associated with resistance. Under SRKN pressure, the group of resistant lines yielded, on average, 19.1 and 23.3% higher than the susceptible lines in 2018 and 2019, respectively. For the susceptible lines, the presence of 1,000 SRKN second‐stage juveniles (J2) in 100 cm−3 of soil negatively affected yield by 6.2%. The presence of the major resistance allele on chromosome 10 reduced yield losses by approximately six‐fold in comparison to the susceptible group which provided significant yield protection under high SRKN pressure. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) generates more damage to soybean [Glycine max (L.) Merr.] than any other parasite in most soybean‐producing countries. The use of SCN‐resistant cultivars remains the most effective method to limit losses caused by SCN. The SCN‐resistant accession PI 88788 has been used almost exclusively to control SCN over the past decades, inducing a shift in nematode virulence to overcome the resistance. Furthermore, PI 88788 and other sources of resistance characterized to date belong to maturity groups (MGs) III and higher, making them less attractive to develop early maturing soybean varieties (MGs 0‐000). In this work, we performed a quantitative trait loci (QTL) analysis of the SCN‐resistant soybean accession PI 494182 (MG 0). A recombinant inbred lines (RILs) population ('Costaud' × PI 494182) segregating for SCN resistance was challenged with SCN (H. glycines [HG] type 0) and genotyped via genotyping‐by‐sequencing (GBS) to produce a genetic map. Six resistance QTL were identified, including a potentially new resistance locus on chromosome 07. A subset of the RIL population was confronted to a HG type 2.5.7 SCN population and some of these exhibited resistance toward this type. Whole‐genome sequencing of PI 494182 and Costaud allowed us to determine the alleles and their copy number for three candidate genes: GmSNAP11, GmSNAP18 (Rhg1), and GmSHMT08 (Rhg4). Finally, we determined that selecting for PI 494182 alleles at some SCN‐resistance QTL could entail linkage drag (decrease in protein concentration and 100‐seed weight, increase in oil concentration). This work provides useful markers for introgressing SCN resistance in early maturing soybean varieties. [ABSTRACT FROM AUTHOR]

Major quantitative disease resistance loci (QDRLs) are rare in the Phytophthora sojae (Kaufmann and Gerdemann)–soybean [Glycine max (L). Merr.] pathosystem. A major QDRL on chromosome 18 (QDRL‐18) was identified in PI 427105B and PI 427106. QDRL‐18 represents a valuable resistance source for breeding programs. Thus, our objectives were to determine its isolate specificity and measure its effect on yield and resistance to both P. sojae and other soybean pathogens. We characterized near isogenic lines (NILs) developed from F7 recombinant inbred lines heterozygous at QDRL‐18; NILs represent introgressions from PI 427105B, PI 427106, and susceptible 'OX20‐8'. The introgressions from PI 427105B and PI 427106 increased resistance to P. sojae by 11 to 20% and 35 to 40%, respectively, based on laboratory and greenhouse assays, and increased yield by 13 to 29% under disease conditions. The resistant introgression from PI 427105B was also effective against seven P. sojae isolates with no isolate specificity detected. Based on quantitative polymerase chain reaction assays, NILs with the susceptible introgression had significantly higher relative levels of P. sojae colonization 48 h after inoculation. No pleiotropic effects for resistance to either soybean cyst nematode or Fusarium graminearum were detected. This information improves soybean breeders' ability to make informed decisions regarding the deployment of QDRL‐18 in their respective breeding programs. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematode species are one of the greatest threats to cause serious yield loss throughout soybean production regions of the United States. Soybean [Glycine max (L.) Merr.] cultivars of different maturity groups carry known resistance to soybean cyst nematode (Heterodera glycines, SCN) at rgh1 and Rhg4 loci. Continuous use of these genes caused SCN population shifts and overcoming host resistance over time. Lack of genetic diversity created a bottleneck in development of new cultivars containing novel SCN resistance genes. Additional sources of resistance to southern root-knot nematode (Meloidogyne incognita, SRKN) and reniform nematode (Rotylenchlus reniformis, RN) could result in supplemental protection of soybean yield. This research focused on determining known and new sources of SCN resistance in 1220 soybean accessions divided into two groups: (i) early-maturity groups (000-II) screened with two SCN populations, and (ii) medium-maturity groups (III-V) screened with six SCN populations. Based on the initial screening results, a subset of 76 accessions was selected for further phenotyping with SCN, SRKN, and RN populations and supplemented by genotyping using molecular markers. The results revealed that 56 lines were resistant to two nematode species in various combinations, and 12 lines were resistant to all three nematode species. Moreover, potential new sources of resistancecarrying genes other than rhg1 and Rhg4 loci were pinpointed. Interestingly, RN resistance highly correlated with rhg1 locus suggesting a common gene or tight linkage. Identified resistant soybean accessions provide promising materials for discovery of novel genes to support cultivar development. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) of soybean [Glycine max (L.) Merr.] causes extensive yield loss, and host resistance has been an effective strategy to minimize this loss. However, shifts in SCN population virulence compatibility have resulted from the extensive use of PI 88788 as a source of resistance in the northern United States. The Northern Regional Soybean Cyst Nematode Tests offer a vast amount of yield testing, combined with resistance screening of entries and the characterization of the SCN infection of test fields. The objectives of this study were to use regional test results (i) to quantify the impact of resistance as the initial field SCN egg counts increase, (ii) to explore effects of maturity group (MG) on resistance, and (iii) to gain insights into how the ability of SCN to infect germplasm with resistance from PI 88788 affects yield. Yield tests across 11 yr were combined into a single dataset with over 1247 test-environment combinations. Analysis of these data showed that the yield advantage of SCN resistant entries increased as initial egg counts increased, and a larger advantage was found in early MGs (00-II) than in later MGs (III-IV). A yield advantage was documented at environments with an initial egg count as low as 100 eggs 100 cm-3 soil. At the levels of SCN infection on PI 88788 found in infested locations, breeding lines with resistance from PI 88788 yielded more than susceptible entries. Analysis of this dataset offers a unique view of the impact SCN resistance provides to soybean. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is a serious pest of soybean [Glycine max (L.) Merr.], in the United States and worldwide. Annual yield losses in the United States are estimated to be more than $1 billion. These losses have remained stable with the use of resistant cultivars, but over time nematodes will adapt to deployed resistance alleles. Currently used resistant cultivars do not have broad resistance. Soybean Plant Introduction (PI) 88788 and its derived cultivars continue to be the primary source of SCN resistance. It is important to identify new accessions with resistance to SCN as the first step to finding new alleles to provide long-term resistance. We have bioassayed in the greenhouse 100 newly available accessions from the USDA Soybean Germplasm Collection. We published methods to bioassay in the greenhouse, including culturing of nematodes to develop near-homogeneous populations for stable reactions on soybeans. Sixty-seven accessions with resistance reaction to Race 2 and/or Race 3 were identified, and SCN resistance was confirmed in replicated multiple tests. Among them, seventeen were yellow seeded. Soybean PIs that were yellow seeded and had resistance to both the races included PIs 512322D, 522186, and 567488B. These are the most desirable sources for development of soybean cultivars with resistance. These soybean lines will be evaluated for their genetic diversity to identify unique types to allow broadening of resistance gene introgression. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe [HG]) is one of the most serious soybean pests [Glycine max (L.) Merr.] worldwide and resistance is controlled by quantitative trait loci (QTL). The fine mapping of new SCN resistance QTL can provide information useful for marker-assisted selection (MAS) in breeding programs and tools for the eventual cloning of the QTL. The objective of this study was to fine map the SCN resistance QTL cqSCN-006 and cqSCN-007 that originated from Glycine soja Sieb. and Zucc. plant introduction (PI) 468916. The fine mapping was done by selecting plants with recombination near these genes and testing progeny of selected plants for resistance to the HG type 2.5.7 SCN isolate PA5 and with genetic markers. For cqSCN-006, 1236 F5 plants and 1662 F6 plants were tested with simple sequence repeat (SSR) markers flanking the QTL, and the progeny from 20 recombinant plants were tested with genetic markers and for SCN resistance. This resulted in the mapping of cqSCN-006 to a 803.4 kb interval on soybean chromosome (chr) 15. For cqSCN-007, 1668 F5 plants were screened with flanking SSR markers, the progeny of 18 recombinant plants were tested, and cqQTL-007 was mapped to a 146.5 kb interval on chr 18. The markers identified in this study will be useful to breeders developing SCN-resistant cultivars and will be highly predictive for determining which plants carry the SCN resistance QTL alleles. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is the most economically important soybean [Glycine max (L.) Merr.] pathogen in the United States. Field SCN populations are adapting to the narrowly based SCN resistance currently deployed in soybean cultivars. The objective of our research was to measure the effects of combinations of SCN resistance genes or quantitative trait loci (QTL) from the wild soybean (Glycine sofa Siebold & Zucc.) Pt 468916 and the domesticated soybean accessions Pt 88788 and P1 437654. Two populations were developed to test the combinations of QTL and genes. Both populations segregated for the G. sofa resistance QTL cqSCN-006 and cqSCN-007. Population 1 also segregated for resistance from P1 88788 and Population 2 segregated for resistance from P1 437654. The populations were tested for resistance to three SCN isolates in a greenhouse and with single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers. In both populations, the two G. sofa resistance alleles significantly increased SCN resistance compared with the alternative alleles. The SCN resistance alleles rhg1 and Rhg4 from PI 437654 and rhg1-b from Pt 88788 also significantly increased resistance compared with the alternative alleles. The two G. sofa QTL alleles significantly enhanced the resistance derived from Pt 88788. These results show that SCN resistance can be increased through stacking genes and QTL from multiple resistance sources. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] yield is often limited by root-infecting pathogens, mainly soybean cyst nematode (SCN; Heterodera glycines Ichinohe). The objective of this experiment was to evaluate differences in root characteristics and yield of NK-S25J5 (SCN-susceptible) and lA2068 (SCN-resistant) soybean cultivars at three locations (De Witt, Nevada, and Whiting) in Iowa, in fumigated vs. nonfumigated soil. A 2-ha section of a field was fumigated each year with Telone-35. Root sampling was conducted at 21, 42, and 63 d after emergence (DAE). Initial SCN population densities (Pi) were 4790, 2590, and 825 eggs 100 cm-3 soil for De Witt, Nevada, and Whiting, respectively. Under the conditions of this experiment, there was no evidence of a decrease in Pi caused by fumigation. Fumigation was associated with an increase in final SCN population (Pf), a reduction in yield of NK-S25J5 by 560 kg ha1 at De Witt, and at 42 DAE, with an increase in root length density (RLD), and root surface area (RSA). The highest yields were obtained at Whiting, the location where the greatest Pf/Pi was observed for NK-S25J5. Average yields for 1A2068 and NK-S25J5 were 4745 kg ha-1 and 3665 kg ha-1, respectively. We concluded that greater RLD could be the result of complex modifications of the environment where roots grow, mainly microbial populations, including SCN. Stress caused by SCN was associated with a decrease in yield in the susceptible cultivar. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (Heterodera glycines Ichinohe) is the most damaging pathogen of soybean [Glycine max (L.) Merr.] in the United States. Observations in fields suggest that high H. glycines population densities are associated with high soil pH, but H. glycines and soil pH have not been linked to soybean yield. The objective of our study was to assess the relationship between soil pH and H. glycines population densities and subsequent effect on yield. Experiments were conducted in Wisconsin from 1997 to 2000 and in Iowa from 1996 to 1998. Results were consistent among the experiments and showed a positive correlation between soil pH and H. glycines population densities and a negative correlation between yield and both soil pH and H. glycines population densities in both states. In the Wisconsin experiment, yield of both H. glycines-resistant and H. glycines-susceptible cultivars decreased as pH increased, but the decrease was less with H. glycines-resistant cultivars. Overall, results indicate that H. glycines population densities and the impact of nematode population densities on soybean yield are related to soil pH; however, the mechanism of these interactions is unknown. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is the most important pest of soybean [Glycine max (L.) Merr.] in the world. A total of 17 quantitative trait locus (QTL) mapping papers and 62 marker-QTL associations have been reported for resistance to soybean cyst nematode in soybean. Conflicting results often occurred. The objectives of this study were to: (i) evaluate evidence for reported marker-QTL associations for resistance to SCN in soybean and (ii) extract relatively reliable and useful information from the reported marker-QTL associations in soybean. A meta-analysis was conducted for QTL locations by comparing the 95% confidence intervals of the reported QTLs. QTLs for different races or different studies were classified into one cluster if their confidence intervals had a region in common. The QTLs of the same cluster may have a shared locus. QTLs for different races or different studies were classified into different clusters if their confidence regions had no region in common and were ≥ 20 cM away from each other. Different clusters may represent different loci. Reported SCN resistant QTLs were classified into three categories: suggestive, significant, and confirmed. Confirmed QTLs are credible and can be candidates for fine mapping and gene cloning. QTLs on linkage groups (LGs) G, A2, B1, E, and J were classified as confirmed. Two clusters of QTLs were identified on LG G. One of them is rhg1. One cluster of QTLs was identified near the end of LG B1, but one QTL may exist around the middle of LG B1. One cluster of QTLs was identified on LGs A2, E, and J, respectively. QTLs on LGs B2, C1, C2, D1a, D2, L, M, and N were classified into suggestive or significant. Confirmation studies are needed to lend credibility for these QTLs. A relationship between soybean QTLs and SCN races is discussed. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN, Heterodera glycines Riggs and Niblack) is the most important soybean [Glycine max (L.) Merr.] pathogen in the USA and its control relies on genetic resistance. When resistance genes from exotic sources are transferred into elite cultivars, deleterious alleles are frequently transferred with resistance through genetic linkages. Two SCN resistance loci have been identified in G. soja Sieb. and Zucc. PI 468916, and the effect these loci have on yield and other agronomic traits is not known. The objective of this study was to determine the effect of each G. soja SCN resistance gene on yield and other agronomic traits in elite soybean backgrounds. These effects were tested in two populations each segregating for SCN resistance derived from G. soja, with one population also segregating for the SCN resistance loci, rhg1, derived from G. max PI 88788. Each population was analyzed for genetic markers linked to the SCN resistance loci and field tested in multiple environments with low to high SCN infestations. The G. soja and rhg1 SCN resistance alleles either had no effect or significantly (P < 0.05) enhanced yield compared with the susceptible alleles. The SCN resistance alleles were also associated with increasing days to maturity, plant height, and lodging scores. Deployment of the G. soja SCN resistance loci will increase the genetic diversity for SCN resistance and will provide breeders with an alternative source of SCN resistance that is not associated with reduced yield. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is a major pest of soybean [Glycine mar (L.) Merr.] in the USA. Soybean plant introduction (PI) 404198A is one of the newly identified sources that can provide a broad spectrum of resistance to SCN. The objective of this study was to identify quantitative trait loci (QTL) associated with resistance to SCN races 1, 2, and 5 in PI 404198A. Linkage groups (LGs) G and A2 were found to be associated with resistance to race 1. QTL on LG G was located on the Satt309-Satt688 region, and it explained a larger proportion of the total variation (20.2%). QTL on LG A2 was located at the Satt424-Satt632-Sat-406 region, and it accounted for a smaller proportion (9%). LGs G and B1 were shown to be associated with resistance to race 2. QTL on LG G was located on the Satt688-Satt309-Satt663 region, and it explained 12.5% of the total variation. Molecular marker Satt453 on LG B1 was found to be associated with resistance to race 2, and it explained 11% of the total variation. LGs G, B1, and N were found to be associated with resistance to race 5. QTL on LG G was located on the Satt688-Satt309-Satt163 region, and it explained 6.3% of the total variation. Molecular marker Satt453 on LG B1 was found to be associated with resistance to race 5, and it explained a larger proportion of the total variation (13%). QTL on IC N was mapped on the Satt584-Sat-280- Satt549, and it explained 9.5% of the total variation. In conclusion, soybean PI 404198A may carry rhg1 on LG G, Rhg4 on LC A2, and a QTL on LC B1. Further studies are needed to lend credibility for QTL on LG N. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) continues to be the most damaging soybean pest [Glycine max (L.) Merr.] in the USA. A major gene that provides partial resistance to SCN is rhg1, which is located on linkage group (LG) G. The objectives of this study were to test the effect of rhg1 on SCN reproduction in both the field and greenhouse and on agronomic traits in the field. Two populations of near isogenic lines (NILs) that segregated for rhg1 were developed to test the effect of the gene. These NIL populations were tested for their ability to support SCN cyst development in a thermo-regulated water bath in a greenhouse and egg production estimated from soil samples taken from each plot in field tests. The NIL populations were evaluated for agronomic traits in field plots to determine the associated effects of rhg1 on these traits. In the greenhouse, NILs predicted to be carrying the resistance allele for rhg1 on the basis of a linked marker supported significantly (P < 0.01) fewer cysts than NILs carrying the susceptibility allele. In field tests, the final egg population density (Pf) was significantly tower and there was a smaller reproductive rate (RI) in NILs carrying the resistance allele at rhg1 than susceptible NILs for both populations across and within environments in 2003. In only one population did the resistant NILs out-yield the susceptible NILs, and this occurred only when the initial SCN pressure was high [>500 SCN eggs (100 cm³ soil)-1. These results show that resistance at rhg1 can have a large effect on SCN reproduction and may result in a significant yield increase. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe), the most destructive pest of soybean [Glycine max (L.) Merrill], is estimated to be responsible for almost nine million megagrams in annual yield loss worldwide. Host plant resistance is the most cost effective and environmentally friendly method of controlling SCN. Resistance is present among soybean plant introductions (Pls) and related wild species, such as Giycine soja Sieb. and Zucc. Molecular marker technology has ushered in a decade devoted to the identification and characterization of quantitative trait loci (QTL) underlying SCN. These genetic mapping efforts uncovered numerous locations of SCN resistance QTL in many Pis. In more than a decade of mapping SCN resistance QTL, there is some consistency in the results. In almost all studies involving various sources of resistance, the QTL conferring the greatest level of resistance mapped to the region conraining rhg1 on linkage group (LG) G. In addition, a major resistance QTL was mapped in many sources to the region containing Rhg4 on LG A2. The mapping of QTL to these regions from many sources suggests that these sources may have resistance genes in common, which has caused concern over the possible dependence on a few resistance genes. Recently, two independent research groups reported cloning candidate genes for rhgl and Rhg4. Despite these advances, there is some degree of trepidation, especially in the public sector, on the use of rhg1 and Rhg4 genetic mapping and cloning information in SCN resistance breeding because of intellectual property issues. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is one of the most destructive soybean [Glycine max (L.) Merr.] pests worldwide. The most common source of SCN resistance used in soy- bean breeding in the northern USA is PI 88788. Previous research has shown that P188788 carries a major quantitative trait locus (QTL) conferring SCN resistance on linkage group (LG) G, which is believed to be rhg1. The objective of our research was to map and confirm additional SCN resistance QTL in Bell, a cultivar with resistance from PI 88788. One hundred four F4-derived fines (F4 population) developed from crossing the cultivars Bell and Colfax were tested for associations between 54 molecular markers and resistance to SCN populations PA3 (HG type 7, race 3) and PAl4 (HG type 1.3.5.6.7, race 14). Three populations of near isogenic lines (NILs) were developed from F4 plants heterozygous for a region on LG J where a significant QTL was identified in the F4 population. The NIL populations were tested with genetic markers and also for resistance to both SCN populations. In the F4 population, SCN resistance QTL were identified at both rhg1 and on LG J. The LG J QTL was confirmed in NIL populations and was given the confirmed QTL designation cqSCN-003. The effect of cqSCN-003 was diminished in the NIL populations compared to the F4 population. This was at least partially the result of segregation distortion in the F4 population between the region containing rhg1 and the region containing cqSCN-003. These results show the importance of verifying QTL in confirmation populations to estimate accurately their effects. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] germplasm PI 437654 exhibits broad resistance to soybean cyst nematode (Heterodera glycines Ichinohe, SCN). Probes derived from PI 437654 bacterial artificial chromosome (BAC) clone 15G19 at the Rhg4 locus detected a restriction fragment length polymorphism (RFLP) between resistant and susceptible germplasms. Detailed RFLP analysis using restriction fragments from BAC clone 15G19 associated the polymorphism with an 8-kb BamHI fragment containing the promoter region and partial coding sequence of a novel soybean subtilisin-like protease, GmSUBI. Complete sequence of GmSUB1 was determined (GenBank AY277949). Regulatory elements for root gene expression, pathogen response, coordinated multiple-gene expression, and a novel 90-bp direct repeat were identified. GmSUB1 shows 74% similarity to Arabidopsis thaliana AIR3. Hybridization analyses indicate that PI 437654 contains only full-length copies of GmSUB1, whereas susceptible germplasm 'Williams 82' contains both full-length and truncated copies of the gene. A 4-fold increase in GmSUB1 copy number, and a corresponding 2- to 3-fold increase in steady state GmSUB1 mRNA levels, was observed in PI 437654 compared with Williams 82. Localization and polymorphism of GmSUB1 within the Rhg4 resistance region, and increases in GmSUB1 gene copy number and expression in PI 437654 compared with Williams 82 infers a functional role in the pathogen response. GmSUB1 is believed to be secreted into the extracellular matrix, and may function in reorganization of cell wall components during plant development and in the defense response. [ABSTRACT FROM AUTHOR]

Identifies markers linked to yield quantitative trait loci in two recombinant inbred line populations segregating for soybean cyst nematode resistance genes. Frequency distribution of mean yield among recombinant inbred line populations; Markers associated with yield among recombinant inbred lines in two soybean populations; Use of bulk segregant analysis.

Examines the effect of crop sequence on soybean cyst nematode and corn yields in Minnesota. Description of the soybean cyst nematode; Determination of egg density at sowing and harvest; Use of nematicide to control different nematodes.

Identifies molecular markers associated with soybean cyst nematode (SCN) resistance loci in a resistance germplasm source, the soybean plant introduction (PI) 89772. Allelic relationships among loci controlling different SCN races; Efficiency of the marker-assisted selection; Bioassays of SCN.

Examines the effectiveness of crop rotation and cultivar resistance in controlling the soybean cyst nematode in full-season and double-cropped soybean. Soybean seed yield; yield components; cyst nematode egg density.

Characterizes transgene expression in soybean cyst nematode (SCN)-infected hairy soybean roots. Evaluation of a transgenic hairy root system for investigations of resistance to SCN; SCN as responsible for significant reduction in soybean yields; Methods used for controlling SCN; In vitro SCN infection.

Presents information on the study conducted on two microsatellites that flank the major soybean cyst nematode (SCN) resistance locus on molecular linkage group (MLG) as it relates to crop science. Methodology used in the study; Detailed information on the results.

Discusses the restriction fragment length polymorphism mapping and marker-assisted selection of soybean cyst nematode (SCN) resistance in PI 209332. Role of SCN in disease problems of soybean; Absence of genetic basis of SCN resistance; Assessment of race-specificities of putative resistance loci in three races of SCN.

Two infectious diseases that cause most yield losses in soybean [Glycine max (L.) Merr.] are soybean cyst nematode (SCN), caused by Heterodera glycines Ichinohe, and sudden death syndrome (SDS), caused by Fusarium solani (Mart.) Sacc. f. sp. glycines (Fsg). Because SCN and SDS have a synergistic effect on yield when they occur jointly in the field, breeders are attempting to develop varieties with dual resistance to these two diseases. Using independent culling as a selection strategy, we screened a set of 31 new soybean plant introductions (PI) that were field evaluated in 1995 at two locations in Southern Illinois. We identified 11 elite PIs that were resistant to SCN race 3, had yellow seed coat, a relatively good field response to SDS, and a moderate seed yield. These superior genotypes can be used as potential parents in soybean breeding programs. [ABSTRACT FROM AUTHOR]

Examines the resistance of 32 soybean plant introductions (PI) to two soybean cyst nematode races (SCN). Bioassays performed in each of the two SCN races; Levels of resistance found on yellow seeded PIs; Desirable sources for development of soybean varieties with resistance to SCN; Fingerprinting of these soybean lines.