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Runkelinis nematodas (Heterodera schachtii) yra polifagas, t.y. turi labai daug augalų šeimininkų. Remiantis literatūros šaltiniais, augalais šeimininkais šiam patogenui gali būti apie 218 augalų rūšių priklausančių 98 gentims. H.schachtii yra vienas labiausiai augalui kenkiančių parazitinių nematodų Europos šalyse (Williamson, Hussey, 1996; Greco, Esmenjaud, 2004; Peterka et al., 2004) ir būtent šis nematodas buvo pirmas patogeninis nematodas, atpažintas cukriniuose runkeliuose (Cooke, 1993). Jis paplitęs visame pasaulyje ir daug cistinių nematodų rūšių patenka į “Schachtii” grupę, kurioje yra apie 20 rūšių (Evans, Rowe, 1998). Visos tirtos vasarinio rapso veislės ‚Ural‘, ‚Terra‘, ‚SW Savan‘, ‚Sponsor‘, ‚SW Landmark‘, ‚Heros‘, ‚Griffin‘, ‚Campino‘, ‚Ability‘ atsparumo H.schachtii patogenui neparodė, tačiau dvi iš jų ‚Liaison‘ ir ‚Maskot‘ buvo patikimai mažiau jautrios patogenui nei kitos. Heterodera schachtii cistų turinys esmingai priklausė nuo vasarinio rapso veislės. Vasarinio rapso veislės ‚SW Savan‘, ‚Griffin‘ ir ‚Ural‘ yra patikimai jautresnės H.schachtii nei likusios tirtos vasarinio rapso veislės vertinant pagal suformuotų cistų turinį. Mažiausias Heterodera schachtii reprodukcijos greitis buvo nustatytas vasarinio rapso veislėse ‚Maskot‘ (0,8), ‚Liaison‘ (0,8) ir ‚Terra‘ (0,9). Šiose veislėse reprodukcijos greičio koeficientas buvo mažesnis už vienetą, tai rodo, kad H.schachtii populiacija neprogresavo. Tačiau nustatyti reprodukcijos greičio koeficiento skirtumai... [toliau žr. visą tekstą] / Beet nematode Heterodera schachtii is polyphagous i.e. it has a lot of host plants. According to literature sources, host plants for this pathogen may be about 218 plants species witch belong to 98 genera. Heterodera schachtii is one of the most harmful parasitical nematodes for plants in European countries (Williamson, Hussey, 1996; Greco, Esmenjaud, 2004; Peterka and others, 2004) and exactly this nematode was the first pathogenic nematode identified in sugar beets (Cooke, 1993). It is distributed worldwide and a lot of cystic nematodes species are included in “Schachtii” group which has about 20 species (Evans, Rowe, 1998). All of investigated summer rape varieties ‘Ural’, ‘Terra’ , ,SW Savan‘, ‘Sponsor‘, ‘SW Landmark‘, ‘Heros‘, ‘Griffin‘, ‘Campino‘, ‘Ability‘ did not show resistance to Heterodera Schachtii pathogen, but two varieties ‘Liaison‘ and ‘Maskot‘ were significantly less susceptible to pathogen than others. The content of Heterodera schachtii cysts was essentially dependent on the variety of summer rape. Summer rape varieties ‘SW Savan’, ‘Griffin’ and ‘Ural’ is significantly more susceptible for Heterodera schachtii in terms of the establishment of cyst contents than the rest investigated summer rape varieties. The lowest Heterodera schachtii reproduction rate has been identified in ’Maskot’ (0.8), ‘Liaison’ (0.8) and ‘Terra’ (0.9) summer rape varieties. In these varieties reproduction rate ratio was less than one and this indicates that Heterodera schachtii... [to full text]

Master of Science / Department of Plant Pathology / Harold Trick / The object of this study was to find a target sequence for the known Heterodera glycines Y25 sequence that contained no homology to any known Glycine max genes so homologous endogenous soybean gene expression will not be effected. In addition, in attempt to improve the accuracy of SCN bioassays performed in greenhouse settings, applications of a variety of insecticides with differing modes of action were applied to screen for any detectable effects on the SCN populations. The full-length sequence of the Y25 gene was blasted against the G. max genome using the National Center for Biotechnology Information blast database and a portion of the gene was found to contained no homology to the G. max genome. A rapid hairy root assay was used to screen for resistance to H. glycines. The sequence was transformed into Agrobacterium rhizogenes using a modified heat shock method. The transformed A. rhizogenes were used to inoculate soybean seedlings. The inoculated seedlings developed hairy roots expressing the target sequence. Upon finishing the hairy root assay it was discovered that there were no detectable differences across any of the treatments or the controls. It was neither proved nor disproved that the new target sequence containing no homology to the G. max genome was as effective as the original target. Further investigation will need to be conducted to show the level of control for the new target sequence.

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.

Le parasitisme est un des principaux problèmes dans les élevages des ruminants. Les nématodes parasites du tractus digestif des ovins et caprins sont responsables d’importantes baisses de rendement. La maîtrise de ces parasitoses a été longtemps basée sur l’utilisation de molécules anthelminthiques. Cependant, l’efficacité des traitements est fréquemment remise en cause par l’émergence d’isolats résistants à une ou plusieurs de ces molécules. Dans ce contexte, une meilleure connaissance des mécanismes impliqués dans l’installation et la survie des parasites dans leur hôte est essentielle pour le développement de méthodes de lutte efficaces. Les P-glycoprotéines sont des pompes membranaires de la superfamille des transporteurs ABC. Ces pompes transportent des molécules très variées qui ont en commun leur caractère hydrophobe. Nous avons émis l’hypothèse de l’implication de ces transporteurs dans l’interaction hôte-parasite. Dans le contexte de ce travail nous avons identifié des séquences partielles ou complètes d’ADNc de 9 Pgps du nématode parasite Haemonchus contortus. Une forte activation des Pgps des nématodes en présence des produits de dégranulation des éosinophiles de l’hôte a été observée, démontrant ainsi l’interaction entre les Pgps des nématodes et les produits issus de l’hôte. De plus, l’exposition in vitro des nématodes parasites aux produits de l’hôte montrent après analyse par PCR quantitative une induction significative de l’expression de deux Pgps (Hco-pgp-3, et Hco-pgp-16). Chez le nématode murin Heligmosomoides polygyrus bakeri 5 Pgps ont été identifiés. D’autre part, l’analyse du niveau d’expression des Pgps d’H. bakeri a permis de montrer que le gène Hba-pgp-2 est exprimé uniquement chez les stades en contact avec les produits de l’hôte (oeufs, L4 et adultes). De plus, une induction spécifique d’Hba-pgp-2 par le cholestérol a été observée suggérant ainsi l’implication d’Hba-pgp-2 dans la capture et/ou la distribution des stérols des cellules de l’hôte indispensable aux nématodes. Ce travail constitue la première mise en évidence de l’interaction entre les Pgps des nématodes parasites et des produits issus de leur hôte. Ces résultats constituent une base solide pour le développement d’une méthode efficace permettant de bloquer ces transporteurs et d’éliminer les nématodes parasites. / Gastrointestinal nematodes cause significant economic loses in goat and sheep livestocks. Control of these parasites is mainly based on anthelmintic treatments. However, the efficacy of these molecules is questioned by the emergence of isolates resistant to one or several antiparasitic drugs. In this context, a better understanding of the mechanisms involved in the nematode parasites establishment and survival in the host is essential for the development of an effective control methods. P-glycoproteins are membrane pumps belonging to the ABC transporter family. These pumps transport a wide range of hydrophobic molecules. In the present study, we hypothesized that in addition to their critical role in xenobiotic resistance, helminth ABC transporters such as P-glycoproteins (Pgps) may also be involved in the transport of host products. Using the sheep parasitic nematode Haemonchus contortus, we investigated the modulation and expression of parasite Pgps activity in response to host eosinophil granule products. These works allowed to identify nine partial or complete H. contortus Pgps. Using a rhodamine efflux assay, we provided functional evidence that host eosinophil granule products can activate Pgps from the parasite suggesting that granule products could act as potential modulators of the ABC transporters activity. We showed by quantitative RT-PCR that among nine different H. contortus Pgp genes; Hco-pgp-3, Hco-pgp-9.2, Hco-pgp-11 and, Hco-pgp-16 were specifically up-regulated in parasitical life stages suggesting a potential involvement of these Pgps during the host-parasite interaction. Using exsheated L3 larvae, we demonstrated that eosinophil granules induced in a dose response manner an overexpression of Hco-pgp-3 and the closely related Hco-pgp-16 gene highlighting the possible involvement of these Pgps in host product transport. . The mice parasitic nematode Heligmosomoides polygyrus bakeri was used for studying the involvement of Pgps in the cholesterol transport. These works allowed identifying five Pgps in H. bakeri. The analysis of the mRNA expression level of H. bakeri Pgps has shown that Hba-pgp-2 gene is expressed only in stages in contact with host products. In addition, a specific induction of Hba-pgp-2 by cholesterol was observed suggesting the involvement of Hba-pgp-2 in the capture and / or distribution of cholesterol from host cells. Taken together, our results provide the first evidence that a subset of helminth Pgps could be involved in the transport of host products. This opens the way for further studies aiming to explore the function of helminth Pgps in host-parasite interactions including host immune response evasion.