Master of Science / Department of Statistics / Perla Reyes / Heterodera glycines, or the soybean cyst nematode (SCN), is a parasite that targets and damages the roots of soybean plants. It is the most yield-limiting pathogen of soybean in the U.S. and the reliable detection and accurate estimation of population densities is crucial to research and management of this pathogen. A study was performed to understand the effects of crop rotation on the prevalence of SCN. Standard sampling procedures in the plant pathology community dictate taking soil samples from potentially infected fields, processing them and counting the number of eggs in one 1 mL subsample via microscope. Suspecting the traditional procedure may lead to invalid results, false negatives in particular, the researcher created and implemented a sampling procedure based on his knowledge of sampling methods and constraints of sampling in the field. Using the data collected, we will discuss the strengths and limitations of the procedure in estimating the population density of SCN in the field. In addition, a simulation study informed by the data will be conducted to determine a sampling strategy that will yield accurate results while still considering the conditions in the field. Knowledge on how the different stages of the sampling procedure for SCN affect the accurate detection of the pathogen would extend to experimental designs and sampling methodologies for other soil dwelling organisms.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 160-168). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 160-168). Also available on the Internet.

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’.

Made available in DSpace on 2015-08-20T17:09:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-23. Added 1 bitstream(s) on 2015-08-20T17:26:30Z : No. of bitstreams: 1 000843133.pdf: 967647 bytes, checksum: 323767d4bfb962e3f0d75dd14629569e (MD5) / A cultura do feijoeiro tem sua produtividade limitada por fatores bióticos, como os fitonematoides. Diversas espécies de têm sido relatadas causando danos à cultura, especialmente aquelas pertencentes ao gênero Meloidogyne. Recentemente, uma nova espécie foi relatada parasitando a cultura no Estado do Paraná, M. inornata. Em função desse relato, o presente trabalho teve como objetivo gerar informações acerca de seu ciclo biológico e sítio de alimentação, sob diferentes temperaturas, comparadas a M. incognita, caracterizar a reação de resistência de 32 cultivares de feijoeiro a M. inornata e verificar o potencial de danos desse nematoide. O teste de reação foi realizado em casa de vegetação, sendo inoculados 2.000 ovos/ planta. Após 50 dias, concluiu-se que todas as cultivares comportaram-se como suscetíveis frente ao nematoide, com FR variando de 13,69 a 94,71, para o grupo cores, e de 17,31 a 80,46, para o grupo preto. O experimento de nível de danos também foi realizado em casa de vegetação, inoculando-se as seguintes densidades populacionais de M. inornata em feijão cv. Tuiuiú: 0 (testemunha); 0,0625; 0,125; 0,25; 0,5; 1; 2; 4; 16; 32; e 64 ovos por cm3 de solo. O limite de tolerância estabelecido para a cultivar Tuiuiú inoculada com M. inornata foi de 9,9 nematoides cm3 de solo, ou seja, a partir dessa densidade populacional a planta passa a ser danificada pelo nematoide. Em relação à biologia comparativa de M. inornata com M. incognita, os experimentos foram realizados em câmara de crescimento do tipo BOD, nas temperaturas, de 18°C, 25°C e 32°C. Os resultados mostraram que temperatura de 25°C é a ideal para o desenvolvimento de ambas as espécies, enquanto aos 18°C, o ciclo de ambas as espécies é retardado e aos 32°C, o ciclo é acelerado; além disso, ambas as espécies formaram um sítio de alimentação permanente semelhante / The culture of the bean has its limited productivity by biotic factors, such as plant parasitic nematodes. Several species have been reported causing damage to the culture, especially those belonging to the genus Meloidogyne. Recently, a new species was reported parasite culture in State of Paraná, M. inornata. Due to this report, the present study aimed to generate information about its life cycle and feeding sites under different temperatures, compared to M. incognita, characterize the resistance reaction of 32 bean cultivars M. inornata and check the potential damage of this nematode. The reaction test was conducted in a greenhouse, and inoculated 2,000 eggs / plant. After 50 days, it was found that all cultivars susceptible behaved as against nematodes, with RF ranging from 13.69 to 94.71 for the color group and 17.31 to 80.46 for the group black. The damage level experiment was also carried out in a greenhouse, the inoculation of the following population densities of M. inornata in bean cv. Tuiuiú: 0 (control); 0.0625; 0.125; 0.25; 0.5; 1; 2; 4; 16; 32; and 64 eggs per cm3 of soil. The tolerance limit set for cultivating Tuiuiú inoculated with M. inornata was 9.9 cm3 of soil nematodes, that is, from that population density the plant becomes damaged by nematodes. Regarding the comparative biology of M. inornata with M. incognita, the experiments were conducted in a growth chamber type BOD at temperatures of 18 ° C, 25 ° C and 32 ° C. The results showed that at a temperature of 25 ° C is optimal for the development of both species, while at 18 ° C, the cycle of both species is retarded and 32 ° C, the cycle is accelerated; Furthermore, both species formed a similar permanent feeding site.

Orientador: Silvia Renata Siciliano Wilcken / Coorientador: Andressa Zamboni Machado / Banca: Antonio Carlos Maringoni / Banca: Dhalton Shiguer Ito / Resumo: A cultura do feijoeiro tem sua produtividade limitada por fatores bióticos, como os fitonematoides. Diversas espécies de têm sido relatadas causando danos à cultura, especialmente aquelas pertencentes ao gênero Meloidogyne. Recentemente, uma nova espécie foi relatada parasitando a cultura no Estado do Paraná, M. inornata. Em função desse relato, o presente trabalho teve como objetivo gerar informações acerca de seu ciclo biológico e sítio de alimentação, sob diferentes temperaturas, comparadas a M. incognita, caracterizar a reação de resistência de 32 cultivares de feijoeiro a M. inornata e verificar o potencial de danos desse nematoide. O teste de reação foi realizado em casa de vegetação, sendo inoculados 2.000 ovos/ planta. Após 50 dias, concluiu-se que todas as cultivares comportaram-se como suscetíveis frente ao nematoide, com FR variando de 13,69 a 94,71, para o grupo cores, e de 17,31 a 80,46, para o grupo preto. O experimento de nível de danos também foi realizado em casa de vegetação, inoculando-se as seguintes densidades populacionais de M. inornata em feijão cv. Tuiuiú: 0 (testemunha); 0,0625; 0,125; 0,25; 0,5; 1; 2; 4; 16; 32; e 64 ovos por cm3 de solo. O limite de tolerância estabelecido para a cultivar Tuiuiú inoculada com M. inornata foi de 9,9 nematoides cm3 de solo, ou seja, a partir dessa densidade populacional a planta passa a ser danificada pelo nematoide. Em relação à biologia comparativa de M. inornata com M. incognita, os experimentos foram realizados em câmara de crescimento do tipo BOD, nas temperaturas, de 18°C, 25°C e 32°C. Os resultados mostraram que temperatura de 25°C é a ideal para o desenvolvimento de ambas as espécies, enquanto aos 18°C, o ciclo de ambas as espécies é retardado e aos 32°C, o ciclo é acelerado; além disso, ambas as espécies formaram um sítio de alimentação permanente semelhante / Abstract: The culture of the bean has its limited productivity by biotic factors, such as plant parasitic nematodes. Several species have been reported causing damage to the culture, especially those belonging to the genus Meloidogyne. Recently, a new species was reported parasite culture in State of Paraná, M. inornata. Due to this report, the present study aimed to generate information about its life cycle and feeding sites under different temperatures, compared to M. incognita, characterize the resistance reaction of 32 bean cultivars M. inornata and check the potential damage of this nematode. The reaction test was conducted in a greenhouse, and inoculated 2,000 eggs / plant. After 50 days, it was found that all cultivars susceptible behaved as against nematodes, with RF ranging from 13.69 to 94.71 for the color group and 17.31 to 80.46 for the group black. The damage level experiment was also carried out in a greenhouse, the inoculation of the following population densities of M. inornata in bean cv. Tuiuiú: 0 (control); 0.0625; 0.125; 0.25; 0.5; 1; 2; 4; 16; 32; and 64 eggs per cm3 of soil. The tolerance limit set for cultivating Tuiuiú inoculated with M. inornata was 9.9 cm3 of soil nematodes, that is, from that population density the plant becomes damaged by nematodes. Regarding the comparative biology of M. inornata with M. incognita, the experiments were conducted in a growth chamber type BOD at temperatures of 18 ° C, 25 ° C and 32 ° C. The results showed that at a temperature of 25 ° C is optimal for the development of both species, while at 18 ° C, the cycle of both species is retarded and 32 ° C, the cycle is accelerated; Furthermore, both species formed a similar permanent feeding site. / Mestre

Molecular diagnostic assays have been developed and utilized to diagnose and to confirm the diagnoses of many plant-parasitic nematodes. We screened several gene sequences of soybean cyst nematode (SCN) [Heterodera glycines, Ichinohen] for their use as molecular markers. A methodology then was developed to use them to detect and quantify the number of H. glycines directly from Mississippi soil. A novel procedure utilizing multiple databases containing nematode DNA and EST sequences was developed to assist in the selection of SCN primers used in the PCR and qPCR assays. In vitro testing demonstrated that the DNA primers and probes developed from the novel procedure for the qPCR assays could accurately detect the presence of SCN. Subsequent testing resulted in a trend of increasing observed numbers of SCN contributing to increasing estimates by qPCR.

Soybean (Glycine max) yield is significantly affected by soybean cyst nematode (SCN), Heterodera glycines, and causes an annual loss of billions of US dollars. In this study, Glycine max xyloglucan endotransglycosylase/hydrolase gene (Gm-XTH52) was transformed into a nematode susceptible G. max [Williams 82/PI 518671] variety of soybean to test whether the protein expression has a role in resistance to H. glycines, and possible chemical changes the expression may cause in the plant composition. Expression level of the Gm-XTH52 gene was three times higher than in controls. Significant reduction in the number of SCN cysts suggested suppression of H. glycines parasitism upon transformation. While total sugar amounts did not significantly differ between the transformed and control plants, xyloglucan amounts of loosely bound sugars of genetically mosaic plants were significantly lower in comparison to controls. Control plants showed lower molecular weight sugars than the transformed plants not subjected to H. glycines infection.

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.

<p>  <em>Heterodera glycines</em> or soybean cyst nematode (SCN) is one of the most yield-limiting soybean plant pathogens. The HG (<em>Heterodera glycines</em>) type test is a greenhouse test to determine the virulence of SCN populations to seven soybean “indicator” lines. Since there has not been a survey of SCN virulence phenotypes in Indiana in over a decade, a total of 124 samples were collected, and all tested positive for SCN. Of 42 selected populations for the HG type test, 88% were virulent to the soybean breeding line PI 88788, from which most SCN-resistant cultivars derive their resistance. All populations were virulent to at least one indicator line, including PI 548402 (‘Peking’), which pose problems for the future of soybean breeding for SCN. <em>Meloidogyne</em> spp. or root-knot nematodes (RKNs) are extremely damaging to agriculture, especially to specialty crops. RKN species are attracted by plant root exudates. The gene expression of <em>M. javanica</em> second-stage juveniles was determined after exposure to tomato root exudates, and the differentially expressed genes were analyzed.</p>