Download or read book Soybean Cyst Nematode Heterodera Glycines Resistance Genes in PI 8972 and PI 209332 Soybean written by M. da S. ASSUNCAO and published by . This book was released on 2000 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean cyst nematode(SCN), Heterodera glycines Ichinohe, is the most serious disease of soybean glycine max(L.) Merr., in the United States and also is a serious pest of soybean on a world-wide basis. The nematode was first found in the United States in North Carolina in 1954 and now occurs in 30 states. Crop rotation plays an important role in controlling the nematode. Control also utilizes different cropping systems and resistant soybean cultivars to supress yield loss caused by H. glycines. A racetest was developed in early 1970's to classify variability in the nematode and was expanded in late 1980's to include 16 races. Eight races have been identified in the United States and in the North Central United States race 3 is the prevalent. Several plants introductions have been found with resistance to the most important races that occur in the soybean production areas in Asia, North America, and South America. The number of resistance genes in PI 89772 and PI 209332 conferring resistance to H.glycines race 3 is not well defined. Crosses of PI 89772 x 'Lee 68', PI 88788 x PI 89772, and Lee 68 x PI 209332 were made in the field and greenhouse. To verify that F1 plants resulted from the cross rather than selfing, simple sequence repeat molecular marker analysis was used to characterize F1 plants and their parents. Several F1 and F2 families from each cross, 98 F3 families from cross PI 89772 x Lee 68, 74 F3 families from cross PI 88788 x PI 89772, and 80 F3 families from cross Lee 68 x PI 209332 were tested with an inbred line of H.glycines developedon 88788. Approximately 8,000 individual plants growing in pots containing 200 cm3 of sterilized soil were inoculated with 4,010 eggs and J2/pot. Thity days after inoculation the number of females that developed on each plant was determined. Cluster analysis revealed sets of families with a low mean number of femalesand low variance, intermediate means and high variance, and high means witha low variance, indicating F3 plants came from, respectively, homozygous resistant, heterozygous or segreganting, and homozygous susceptible F2 plants. Thus, resistance classes were considered as quantitative parameters having different levels of resistance as opposed to only two classes, either or susceptible. Chi-square analysis of segregation of phenotypic data indicated two genes confer resistance torace of H.glycines. One gene acts as a major gene (Rhgx) and the other a minor gene (Rhgy) in conferring resistance of the parents PI 89772 (Rhgx1?Rhgx1?Rhgy1?Rhgy1?) PI 88788 (Rhgx2?Rhgx2?Rhgy2?Rhgy2/), and PI 209332 (Rhgx3?Rhgx3?Rhgy3?Rhgy3) to H.glycine race 3. The same genes may occur in PI 209332 as in PI 89772, but support for this hypothesis must be obtained by studying the cross PI 209332 x PI 89772. The same major (Rhgx) and minor (Rhgy) genes occur in PI 89772 (Rhgx1?Rhgx1?Rhgy1?Rhgy1?) and PI 88788 (Rhgx2?Rhgx2?Rhgy2?Rhgy2?). The phenotypic ratios obtained in this research indicate that epsitasis occurs between loci Rhgyx and geney.

Download or read book Soybean Cyst Nematode Heterodera Glycines Resistance Genes in PI 89772 and PI 209332 Soybean written by Mauricio da Silva Assunc̦ão and published by . This book was released on 2000 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Resistance to Heterodea Glycines scn in Soybean Plant Introductions pi 467312 and 507354 written by Peiqin Lu and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean cyst nematode (SCN) Heterodera glycines Ichinohe is the most serious pest of soybean [Glycine max (L.) Merr.] in the world. The effectiveness of breeding soybean SCN resistant cultivars is reduced by the variation of SCN population and narrow genetic basis of resistant soybean cultivars. Hence, it is important to investigate new soybean SCN resistant sources for new genes that confer resistance to SCN field populations such as HG type 1.2.7 to provide durable resistance. Soybean plant introductions PI 467312 and PI 507354, are unique, with resistance to SCN multiple HG types respectively. However, the genetic basis of SCN resistance in these PIs is not known. The objectives of this study are to investigate the inheritance of resistance to SCN HG types 0, 1.2.7, and 1.3.6.7 in PI 467312 and the SCN resistance to SCN HG types 2.5.7 and 1.2.7 in PI 507354, to identify and map quantitative trait loci (QTL) associated with resistance to SCN HG types 0, 1.2.7, 1.3.6.7 in PI 467312 and resistance to SCN HG types 2.5.7, and 1.2.7 in PI 507354. The study showed that resistance to HG types 1.2.7, and 1.3.6.7 in Pop 467 were conditioned by one dominant and two recessive genes (Rhg rhg rhg) and resistance to HG type 0 was controlled by three recessive genes (rhg rhg rhg). Resistance to both HG types 2.5.7 and 1.2.7 in Pop 507 fit a one dominant and 3 recessive gene model (Rhg rhg rhg rhg). Two to three QTLs were associated with resistance to each HG type (race) in both populaitons.

Download or read book Biology and Management of the Soybean Cyst Nematode written by Robert D. Riggs and published by American Phytopathological Society. This book was released on 1992 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1 History, distribution, and economics. 2 Systematics and morphology. 3 Epiphytology and life cycle. 4 Cellular responses to infection. 5 Population dynamics. 6 Genetics. 7 The race concept. 8 Nematode race identification, A look to the future. 9 Interactions with other organisms. 10 Host range. 11 Chemical control. 12 Management by cultural practices. 13 Biological control. 14 Breeding for resistance to soybean cyst nematode. 15 Cytopathological reactions of resistant soybean plants to nematode invasion. 16 Tolerance in soybean.

Download or read book Diversity and Virulence of Soybean Cyst Nematode Heterodera Glycines Ichinohe in Nebraska written by Kyle C. Broderick and published by . This book was released on 2016 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is one of the most economically important soybean pathogens in the United States. Best management practices are the use of resistant cultivars and crop rotation. Though there are several genetic sources of SCN resistance, most of the SCN-resistant cultivars are derived from a single resistance source (PI 88788). Other states have reported an increase in virulence to PI 88788 due to prolonged use of this resistance. In this thesis, two studies were conducted to characterize the diversity and virulent phenotypes of SCN populations in Nebraska. The first study assessed the virulent phenotypes of SCN field populations and their diversity in Nebraska by conducting HG type tests on 118 populations from 36 soybean-producing counties. 46.6%, 29.7%, and 88.1% of populations were virulent on PI 88788, Peking, and PI 548316 resistance respectively. No populations were virulent on PI 437654 (Hartwig). Virulence to PI 88788, PI 209332, and PI 548316 was common and found in nearly every county. Many counties also had populations virulent on Peking, PI 90763, and PI 89772. The second study investigated the mitochondrial diversity of SCN in Nebraska as well as the diversity within a field. Previous work examining the haplotype diversity of SCN using CO1 mitochondrial markers found low diversity and two primary haplotypes – one common and found throughout the U.S. while the second, the MNNE haplotype, was only found in Minnesota and northeast Nebraska. Markers were developed to determine if there is association of the MNNE haplotype with HG type and the incidence of the MNNE haplotype in Nebraska. No association was found between the MNNE haplotype and HG type. Populations from the original Nebraska field did not contain the MNNE haplotype, however it was confirmed to be in the original isolates suggesting the MNNE haplotype is found at very low frequencies in the field. Information on virulence and diversity of SCN in Nebraska will provide insight for development and selection of SCN resistant cultivars.

Download or read book Identifying the Genetic Determinants for Virulence in the Soybean Cyst Nematode Heterodera Glycines written by Dave T. Ste-Croix and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The soybean cyst nematode (SCN - Heterodera glycines) is the most economically important pathogen affecting soybean crops, causing significant reductions in yield on a global scale. Currently, the primary method for the management of this destructive root parasite is by utilizing natural host resistance. There are two main sources of genetic resistance commonly used in commercial practices to mitigate these losses: soybean plant introductions (PI) 548402 (Peking) and PI 88788. However, in North America, over 95% of resistant soybeans derive their resistance from PI 88788 genetics. Although still effective to a large extent, prolonged exposure to these limited genetic sources has led to the emergence of virulence within the SCN population, with subpopulations of nematodes now capable of overcoming host resistance. Given that soybean is expected to become one of the most economically significant grain crops in Quebec and Canada, it is crucial to understand how these nematodes overcome resistance. To gain insights into the genetic basis of virulence, a comparative transcriptomic analysis was conducted on individual nematodes isolated from multiple SCN populations with varying degrees of virulence against both main sources of resistance. By comparing the gene expression profiles of females categorized by their virulence phenotypes, we observed a significantly different transcriptomic response in females developing on Peking compared to those developing on PI 88788 or the susceptible control Essex. Indeed, overexpression and repression was observed in multiple effector genes of females developing on Peking. Further sequence analysis of expressed genes in Peking virulent nematodes also revealed a wide array of sequence polymorphisms and differential exon usage not shared by PI 88788 virulent or avirulent nematodes. Building upon the findings of potential alternative splicing in effector genes, a de-novo genome-guided transcriptome was generated in chapter two using long reads sequencing generated from single nematodes. This analysis aimed to assess the presence and extent of alternative splicing within effector genes and, more broadly, the SCN transcriptome. By comparing the expression profiles of these transcripts in PI 88788 virulent and avirulent females from different populations, simultaneously selected on both cultivars, two promising novel effector gene candidates (Hg-CPZ-1 and Hg16414.1) were identified, along with six other overexpressed effector candidates common to all virulent females from PI 88788. Although the two first chapters identified multiple candidate effectors associated with Peking and PI 88788 virulence, the regulatory mechanisms controlling these effectors remained unknown. Consequently, the third chapter explored the SCN microRNAs (miRNA) characterizing candidates potentially involved in the post-transcriptional regulation of effector genes. A comprehensive analysis of whole-nematodes and exosome-derived miRNAs revealed a diverse set of species- and lineage-specific candidates characterized for the first time in the SCN. By utilizing animal-specific and plant-specific miRNA target predictors, a subset of these miRNAs were also predicted to interact with nematode effectors and soybean resistance-related genes emphasizing the complex nature of SCN parasitism through the potential ability of nematodes to not only regulate its effectors genes but also its host genes. In summary, the findings from these chapters have not only enhanced our understanding of the mechanisms underlying the evolution and regulation of effector genes but also provide potential targets for improving resistance against SCN and detecting the presence of this destructive root parasite more effectively.

Download or read book On the Pathogenesis of Soybean Cyst Nematode and Mechanisms of Resistance by Soybean written by Vincent Colantonio and published by . This book was released on 2017 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is the most devastating pathogen of soybeans, Glycine max (L.) Merr., causing over $1 billion in yield losses annually in the United States alone. Currently, planting of genetically resistant cultivars is the most commonly employed management strategy. Due to an overuse of genetic resistance derived from the soybean variety 'PI 88788', many populations of soybean cyst nematodes are becoming virulent on previously resistant cultivars, urging the understanding and discovery of alternative mechanisms of SCN resistance. In this study, we will delve into the history and epidemiology of Heterodera glycines, learn about the molecular etiology underlying SCN pathogenesis, begin to understand the mechanism of resistance by Peking-type soybeans, and look to discover a novel mechanism of resistance by establishment of a mutagenized population of the soybean variety 'PI 567516C'.

Download or read book Genetic and Molecular Analysis of Soybean Cyst Nematode Virulence written by Michael N. Gardner and published by . This book was released on 2017 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: The soybean cyst nematode (SCN) Heterodera glycines is the most economically important pathogen of soybean, capable of causing large scale yield loss on a global scale. Current management practices utilize host resistance, but commercial resistance is limited to three main sources, the soybean plant introductions (PI) 54802 (Peking), 88788, and 437654. More than 95% of soybean grown in the north central United States have resistance derived from PI 88788 and repeated use of this resistance has led to the development of highly virulent nematode populations capable of infecting these resistant plants and causing yield losses. In order to identify the mode of inheritance for virulence on the three primary sources of resistance to SCN a controlled crossing study was performed, mating a highly virulent nematode (TN20) with an avirulent nematode (PA3). By monitoring the offspring of this cross it was found that depending on the source of host resistance, virulence is inherited in a dominant or a recessive manner except for virulence on PI 437654, which is likely a multigenic trait dependent on multiple recessive genes. A de novo transcriptome assembly was then generated for SCN and mined for novel stylet-secreted effectors, identifying a new pool of candidates that may play a role in virulence. Finally, a comparative transcriptomic analysis was performed across multiple SCN populations to identify conserved expression patterns and genes associated with virulence. Results from these studies will be used to improve current management practices for SCN and provide new potential targets for improving SCN resistance.

Download or read book Characterization of Soybean Cyst Nematode Diversity in Kansas written by Pamela Ann Rzodkiewicz and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The soybean cyst nematode (Heterodera glycines) (SCN) is an important pathogen of soybean in the United States. Annual yield losses from SCN are estimated to be over $2 billion worldwide. However, SCN virulence or the ability of a nematode to grow on resistant soybean genotypes varies widely among SCN populations. Fortunately there are several genetic sources of resistance to decrease the virulence of the pathogen on soybean. The objectives of this research were to: 1) characterize the genetic diversity of soybean cyst nematode populations in Kansas, 2) determine the frequency of Kansas SCN populations virulent on PI88788, 3) determine which plant introductions used in the HG Type Test provide the best level resistance, and 4) compare the performance of commercial soybean cultivars to the plant introduction from which their SCN resistance was derived. Soil samples were collected from SCN-infested fields across the state. Each soil sample was taken to the greenhouse and planted to a susceptible soybean cultivar to increase SCN population. Following an SCN population increase, a HG Type Test was planted. H. glycines field populations were highly variable, not only in population densities, but also in their abilities to develop on soybean genotypes. Collected from a diverse range of environments, ten HG types were identified. About 50% of the H. glycines populations were virulent on PI 88788, and most of the populations were virulent on commercial SCN resistant lines which derived their resistance from PI 88788. The commercial lines tended to be more susceptible to SCN than the lines from which they derived their resistance, but few HG populations were virulent on PI 437654 or the commercial line that derived its resistance from PI 437654. These results suggest that sources other than PI 88788 should be used in the development of H. glycines resistant cultivars for Kansas. One possible source of resistance is PI 437654. Information about SCN diversity in Kansas will improve decisions regarding cultivar development and selection for SCN management.

Download or read book Investigating Soybean Cyst Nematode Resistance written by Katelyn Butler and published by . This book was released on 2018 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean cyst nematode (SCN; Heterodera glycines) is consistently ranked as the most economically damaging pathogen of soybean, a globally important oilseed and protein crop. To manage this persistent pathogen, growers rely primarily on crop rotation and genetic resistance. For decades, Rhg1 has been the primary resistance locus deployed in most commercial soybean varieties. Resistance at Rhg1 is conferred by three types of gene products not previously known to mediate plant defense. Gene copy number variation and expression/localization differences contribute to this resistance. In the present work we demonstrate that Rhg1 can also confer resistance in potato and Arabidopsis against the cyst nematodes Globodera pallida, Globodera rostochiensis and Heterodera schactii. This supports the hypothesis that Rhg1 evolved to interfere with conserved cyst nematode infection processes. This finding suggests biotechnology-based management strategies for cyst nematodes in other crops. SCN evolution necessitates new resistance sources in soybean. The remainder of this thesis describes the identification and characterization of novel resistance genes from two independent SCN resistance QTL originating from Glycine soja accession PI 468196, cqSCN-006 and cqSCN-007. I discovered that altered regulation of a ɣ-SNAP protein encoded at cqSCN-006 confers resistance. An [alpha]-SNAP protein contributes to Rhg1-mediated resistance, underscoring the importance of SNAP proteins and their associated activity in cyst nematode pathogenesis. cqSCN-006 resistant plants exhibit differential accumulation of the ɣ-SNAP protein and expression of alternative splice forms at infection sites. Little is known about the function of ɣ-SNAPs in any system, and even less in plants. I have identified a role of ɣ-SNAPs in SCN response. I also report progress towards identifying the gene encoding resistance at G. soja QTL cqSCN-007. While no gene(s) has been confirmed to confer resistance, a RAD21-like gene is the strongest candidate. The upstream region of the resistant allele contains a large deletion and exhibits differences in gene expression. Studies of cyst nematode resistance continually expand plant defense paradigms. The work in this thesis reveals additional intricacies of this pathosystem, laying the groundwork for further exploration of soybean-SCN interaction and improved plant protection strategies.

Download or read book Identification and Characterization of Soybean Cyst Nematode Resistance Genes Using DNA Markers written by Vergel Cierte Concibido and published by . This book was released on 1995 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Molecular Characterization of Genetic Resistance to Soybean Cyst Nematode in Soybean Line SS97 6946 written by Md Sariful Islam and published by . This book was released on 2008 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean Cyst Nematode (SCN) (Heterodera glycine) is the most damaging pest of soybean and estimated annual yield losses are 1.5 billion dollars in USA. Breeding resistant cultivars is the most efficient means to control SCN but the nematode has adapted and overcomes resistance of developed soybean cultivars due to a narrow genetic base. A study was initiated in summer 2007 to investigate the genetics of resistance to SCN and identify Quantitative Trait Loci (QTL) conferring broad-spectrum SCN resistance in SS97-6946. Leaves of 160 F2 individuals from the cross PI 567476 X SS97-6946 were collected to isolate DNA in summer 2007. Three hundred forty seven polymorphic Single Sequence Repeat primer pairs out of 547 were used to genotype the F2 plants. Seeds from 160 F2:3 families were evaluated against races 1, 2, 3 and 5 for SCN bioassay following standard protocol. The ratio observed between resistant to susceptible F2:3 families revealed that SCN resistance involved three recessive genes for both race 1 and 2; two dominant and one recessive for race 3; one dominant and two recessive for race 5. Three markers mapped on linkage groups (LG) A2, E, and G and accounted for 33.8% of the total phenotypic variance for resistance to SCN race 1. One resistant QTL was detected on LG A1 accounted for 18.8% of the total phenotypic variance of race 2. Three markers mapped on LGs A2, G, and M to be associated with resistance to SCN race 3 and shared 24.9% of total phenotypic variance. Three markers on LG G alone and four markers on LGs A1, B2, M, and O were mapped and shown to be linked with SCN resistance to race 5 and accounted for 70.8% of the total phenotypic variance.

Download or read book The Inheritance of Resistance of Soybeans to the Soybean Cyst Nematode Heterodera Glycines written by Billy E. Caldwell and published by . This book was released on 1959 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigating Root knot and Soybean Cyst Nematode Parasitic Interactions Through Transcriptomic Analyses of the Host and Parasite written by Ellie Walsh and published by . This book was released on 2016 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plant-parasitic nematodes are a major threat to global agricultural production. Root-knot nematodes (RKN, Meloidogyne spp.) are arguably the biggest threat, capable of parasitizing virtually every crop. Soybean cyst nematode (SCN; Heterodera glycines) has a narrow host range, but is the most destructive pathogen of a particularly important crop, soybean (Glycine max). RKN’s wide host range makes crop rotation often inadequate for management, and host resistance is unavailable in many crops. Effective resistance is available against SCN however populations have adapted to the most frequently used sources of resistance. RKN and SCN both induce elaborate feeding sites. In addition to being the sole source of nutrition, the feeding sites are the primary targets of nematode secretions to manipulate host cellular functions; consequently, they are very important interfaces of the interaction. The general aim of this research was to elucidate changes in the transcriptome underlying the successful interaction between these nematodes and their hosts. Although the use of RNA interference (RNAi) to knockdown nematode genes is actively being pursued as a new strategy for nematode control, little is known about the effects of general RNAi mechanisms during parasitism. As the suppression of RNAi has been characterized in other pathosystems, I hypothesized that parasitic nematodes may also be influencing these pathways. Tanscriptomic analysis of genes associated with RNAi machinery and target genes indicates that RNAi-regulated pathways are altered during the parasitic interaction. Using a silenced reporter gene, I found the disturbance to be specific to the nematode feeding site. Furthermore, disrupting these pathways with viral suppressors of RNAi renders the host more susceptible to nematode parasitism. Transcriptomic analysis indicates that this effect extends into later stages in parasitism, making the adult female stage of particular interest for further analyses. I performed a transcriptomic analysis of adult female RKN to address the hypothesis that transcriptional patterns in this later stage of parasitism will reveal new candidate genes encoding proteins that regulate the parasitic process, such as proteins that interact with RNAi among other plant pathways. Results from RNA-Seq analysis and reverse transcriptase PCR indicate that cell wall modifiers likely continue to play an important role in the parasitic interaction. Results from transcriptomic analysis including the putative secretome have highlighted new candidates for functional analysis to determine their role in the interaction. The later stage in parasitism is similarly of interest in SCN. SCN populations are adapting to the most commonly planted host resistance available in soybean, derived from Plant Introduction (PI) 88788 and “Peking.” The resistance response in PI 88788 appears to be longer-lasting than that in Peking, which impacts nematodes’ early development. Due to my focus on the adult female stage, I chose to investigate parasitism on PI 88788. I hypothesize that transcriptional differences between females from populations avirulent and virulent on PI 88788 may play a role in their adaptation to resistance. Results from this study indicate that the expression of an effector-like gene may have been lost in virulent populations, presumably allowing them to evade host detection and subsequent defense responses.

Download or read book An Analysis of Signaling Processes Leading to a Defense Response in Soybean written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Plant-parasitic nematodes are the cause of devastating yield loss in vital agricultural crops around the world. Heterodera glycines , also referred to as soybean cyst nematode, is the main pathogen of Glycine max (soybean) causing more loss than all other pathogens of G. max combined. The resultant economic impact due to H. glycines in United States soybean production alone is estimated to account for an annual one-billion-dollar loss. Natural resistant genotypes have been found in trials to combat this pathogen. Of the resistant varieties identified, G. max [Peking/PI 548402] and G. max [PI 88788] are the major sources of resistance. Identification of genes expressed in the cells of which the nematode parasitizes, the syncytia, exclusively undergoing the resistant/incompatible reaction from the two major sources of resistance mentioned previously have identified a number of candidate genes presumed to function in defense to H. glycines parasitism. Prior to this work, success has been obtained by selection of a number of these candidate genes in functional analysis to show involvement in defense. This work is aimed at functionally identifying signaling components involved in the defense reaction. Reverse genetic studies of NON-RACE SPECIFIC DISEASE RESISTANCE 1 Glycine max homolog, Gm-NDR1-1, has confirmed a functional role in the defense to H. glycines to G. max. Gene expression studies revealed both effector-triggered immunity (ETI) and pattern-triggered immunity (PTI) components to be regulated by Gm-NDR1-1. Furthermore, induction in the heterologous expression of Gm-NDR1-1 in Gossypium hirsutum (cotton) suppressed Meloidogyne incognita parasitism. Harpin treatment has been evaluated due to the knowledge of NDR1s capability of being harpin-induced (HIN1). Expression studies of the harpin treatment did in fact induce Gm-NDR1-1. The analysis further provides ev

Download or read book Molecular Markers for Resistance to Soybean Cyst Nematode Heterodera Glycines I in Soybean Glycine Max L Merr written by Ramamurthy Mahalingam and published by . This book was released on 1994 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Heterodera Glycines Macrophomina Phaseolina Interactions on Soybean written by Horacio Daniel Lopez Nicora and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: oth Heterodera glycines, the soybean cyst nematode, and the fungus Macrophomina phaseolina, the causal agent of soybean charcoal rot, are damaging soil-borne pathogens. Many studies have been conducted to understand the individual effect of each pathogen on soybean. Little is known, however, of the effect when both soil-borne pathogens co-infest soybean fields. We examined this effect in three different studies. The first was a survey to determine the distribution and abundance of both pathogens in agricultural fields across Ohio. Soil samples were collected from soybean fields; H. glycines and M. phaseolina were extracted and quantified from each soil sample. More than 77% of the samples tested positive for the presence of both pathogens. Surprisingly, over 75% of the growers with H. glycines infested fields were unaware they had this problem. Information on the distribution and abundance of these pathogens in Ohio is extremely useful for alerting growers of potential yield reduction and recommending integrated pest management. In the second study, fields with different levels of each pathogen were identified during three growing seasons. From each field, soybean yield and abundance of H. glycines and M. phaseolina were obtained and used in a spatial regression analysis. We evaluated the effect of each pathogen and their interaction on soybean yield. Based on spatial regression analysis there was a significant interaction effect between H. glycines and M. phaseolina on soybean yield for fields with high initial inoculum. Observations from these fields helped us design the third study in which we expanded on basic nematology and plant pathology techniques, and used plant genetics to evaluate and better understand the field biology of these soil-borne pathogens. Experiments were conducted in the greenhouse and in two fields infested with H. glycines (HG) Type 2.5.7 and M. phaseolina in 2013 and 2014, respectively. Soybean lines developed through four backcrosses (BC4) were used; half of the lines were predicted to have the H. glycines resistance allele at Rhg1 from PI 88788 based on a linked genetic marker and the other half did not have the resistance marker. In a split-plot experimental design, soybean genotypes were planted in adjacent plots, one with M. phaseolina added pre-plant and the other without. Soybean yield reduction took place with increasing levels of H. glycines initial population in both fields. In addition, soybean emergence in plots infested with M. phaseolina was reduced by over 10% and 35% compared with uninfested plots in the 2013 and 2014 field experiments, respectively. Results from these studies showed that the marker alleles of lines for Rhg1 and the greenhouse studies reliably predicted the response of soybean lines to HG Type 0 and HG Type 2.5.7. In the field studies, however, the response of these lines to HG Type 2.5.7 was dependent on H. glycines initial population. Environmental conditions in 2013 and 2014 were not conducive for the development of charcoal rot and the disease did not develop. The findings of these projects will help improve integrated pest management recommendations to growers for sustainable crop production.