Download or read book Variation and Genetic Studies in the Soybean Cyst Nematode Heterodera Glycines written by Constatinos Nicholas Koliopanos and published by . This book was released on 1970 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 DNA Markers and Genetics of Resistance to Cyst Nematode and Seed Composition in Soybean Peking X Essex written by Boxing Qiu and published by . This book was released on 1998 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean [Glycine max (L.) Merr.] is one of the major crops in the USA and worldwide. Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, causes severe damage to soybean production. In 1988, the SCN was ranked as the number one crop disease in the southern USA. To combat this pest, genetic characterization of the resistance genes to SCN and molecular approaches for tagging the resistance genes have recently been conducted. The cultivar 'Peking' is one of the most important resistance sources to SCN. It gives resistance to SCN Race Isolates 1, 3, and 5. The genetic inheritance for resistance to SCN Race 3 in Peking was studied in the past decades, but the resistance nature is complicated and the inheritance patterns for resistance to SCN Races 1 and 5 were not well documented. In this study, F 1, F 2, and F 2:3 subfamilies were used for studying the genetic background of the SCN resistance in Peking. It was discussed that resistance to SCN Races 1, 3, and 5 each were conditioned by a three-gene model, one dominant and two recessives (Rhg, rhg, rhg). The complexity of SCN multiple resistance genes in soybean and the heterogeneity of indigenous field SCN Race populations make it difficult to breed resistant soybean cultivars. Both morphological and molecular markers that are associated with the resistance to SCN are known to play an important role in tagging and transferring resistance genes from wild types into soybean cultivars. Black seed-coat color was previously reported as a morphological marker linked to SCN resistance. Our data indicated that the reddish brown seed-coat color was linked to the loci controlling resistance to SCN Race 3. The mean of the Index of Parasitism (IP) in reddish-brown seed-coat color plants was significantly less than one in the plants with black seed coat color. DNA markers associated with resistance to SCN Race 3 have been documented by a number of scientists. Restriction fragment length polymorphism (RFLP) analysis was used as a molecular marker-mediated approach to identify the markers for SCN resistance in this study. Based on the co-segregation between phenotypic SCN reactions in 200 F 2:3 families and RFLP scoring data from 200 F 2 plants, five DNA markers, A593 and T005 on linkage group (LG) B, A018 in LG E, and K014 and B072 on LG H, were associated with resistance loci for SCN Race 1, which jointly explained 57.7% of the phenotypic variation. Three markers (B072 and K014 on LG H, T005 on LG B) were linked to resistance loci for Race 3, and together explained 21.4% of the total phenotypic variation. Two markers (K011 on LG I, A963 on LG E) associated with resistance to Race 5 jointly explained 14.0% of the total phenotypic variation.

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 Plant Nematode Interactions written by and published by Academic Press. This book was released on 2015-03-26 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Botanical Research publishes in-depth and up-to-date reviews on a wide range of topics in plant sciences. Currently in its 73rd volume, the series features several reviews by recognized experts on all aspects of plant genetics, biochemistry, cell biology, molecular biology, physiology and ecology. This thematic volume features reviews on molecular and developmental aspects of the compatible plant-nematode interaction. The contributors all actively work in the field of molecular genetics and genomics of plant parasitic nematodes and nematode feeding sites. Reviews focus on molecular and physiological aspects of nematode feeding site development and includes specific chapters on nematode effectors as well as plant responses. Publishes in-depth and up-to-date reviews on a wide range of topics in plant sciences This volume features reviews of the fast moving field of compatible interaction between plants and sedentary endo-parasitic nematodes A strong focus on molecular and physiological aspects of nematode feeding site development and includes specific chapters on nematode effectors as well as plant responses

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 An Investigation of Heterodera Glycines Populations on Resistant Soybean written by Alison Lee Colgrove and published by . This book was released on 2004 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of the soybean cyst nematode, Heterodera glycines, on resistant soybean was investigated in three separate studies: (1) the effect of soybean resistance on field populations of H. glycines ; (2) the effect of resistant soybean on males of H. glycines populations; and (3) a molecular analysis of H. glycines development on resistant soybean and sex determination. The response of field populations to consistently planted resistant soybean was observed to determine if H. glycines race test results are reliable indicators for future population changes. Results suggested that race test results are highly variable and of questionable value for forecasting. Variability of sex ratios on resistant soybean was investigated in inbred lines of H. glycines in which reproduction of females is consistent in an attempt to characterize resistance effects on H. glycines males. Results suggested that the lower requirements for male survival under stressful host conditions and not environmental sex determination mechanisms were associated with higher male numbers. A molecular analysis of inbred lines of H. glycines compared the DNA of lines with different levels of development on resistant soybean and males and females in an attempt to identify genetic markers for virulence and genetic differences between males and females. Polymorphisms found between virulent and avirulent lines are useful to characterize H. glycines development on resistant soybean.

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 Identifying the genetic determinants for virulence in the soybean cyst nematode Heterodera glycines written by Dave Thibouthot-Ste-Croix and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Résumé en anglais

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 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 Studies on the Soybean Cyst Nematode Heterodera Glycines and Its Injury to Soybean Plants in Japan Classic Reprint written by Minoru Ichinohe and published by Forgotten Books. This book was released on 2017-11-19 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Studies on the Soybean Cyst Nematode, Heterodera Glycines and Its Injury to Soybean Plants in Japan The yellow dwarf disease caused by the soybean-cyst nematode appears in fields toward the middle of July, about 2 months after sowing. It is characterized by severe retardation of growth, stunting, and yellowish appearance on the aerial parts of the plants. The foliage of the diseased plant falls off early. The plant bears only a few flowers, and a few seeds which are smaller in size and inferior in quality to the normal ones. The roots of affected plants bear many developed lateral rootlets and in most cases many fewer bacterial nodules than those of healthy plants. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

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 Studies on the Soybean Cyst Nematode Heterodera Glycines written by Minoru Ichinohe and published by . This book was released on 1960 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Functional Analysis Identifies Glycine Max Genes Involved in Defense to Heterodera Glycines written by Prachi D. Matsye and published by . This book was released on 2013 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: The infection of plants by Heterodera glycines, commonly known as soybean cyst nematode (SCN), is a serious agricultural problem of worldwide extent. Meanwhile, it provides an excellent experimental model to study basic aspects of how cells function, in particular, during biotic challenge. Heterodera glycines challenges plant cells by initiating, developing and sustaining an interaction that results in the formation of a nurse cell from which the nematode derives nourishment. The presented experiments examine (1) how a cell can be de-differentiated and reprogrammed to perform a much different biological role and (2) how a cell’s immune responses can be engaged or suppressed to accomplish that goal. The observation of alpha soluble N-ethylmaleimide-sensitive factor attachment protein (alpha-SNAP) expression, its location within the rhg1 locus and known involvement in the vesicular transport machinery relating to defense made it a strong candidate for further functional analysis. Functional studies demonstrated that overexpression of alpha-SNAP in the susceptible G. max[Williams 82/PI 518671] genotype that lacks its expression results in the partial suppression of H. glycines infection. This indicated that the vesicles could be delivering cargo to the site of infection to engage a defense response. High levels of expression of a cell wall modifying gene called xyloglucan endotransglycosylase also occur during defense. XTHs associate with vesicles, act in the apoplast outside of the cell, and have a well-known function in cell wall restructuring. These observations indicated that alterations in the cell wall composition of nurse cells could be important for the successful defense response. Overexpression of a G. max xyloglucan endotransglycosylase (Gm-XTH) in the susceptible G. max[Williams 82/PI 518671] genotype resulted in a significant negative effect on H. glycines as well as R. reniformis parasitism. The results, including preliminary experiments on components of the vesicle transport system, identify a potent mechanism employed by plants to defend themselves from two types of plant-parasitic nematodes.