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Einleitung: Der frühzeitigen Detektion pulmonaler Rundherde kommt eine Schlüsselrolle bei neoplastischen Erkrankungen von Hund und Katze zu, indem sie maßgeblich Prognose und Behandlungsoptionen beeinflusst. Ziel unserer ersten Studie war, die aktuelle diagnostische Wertigkeit und mögliche Limitationen der klassischen Röntgenuntersuchung bei der Detektion pulmonaler Rundherde darzustellen. Unsere zweite Untersuchung beschäftigt sich mit dem Ziel der computerassistierten Detektion (CAD) und deren Einsatz in der Tiermedizin. Material und Methoden: Der Untersuchungszeitraum umfasste die Jahre 2005–2011. In die erste Studie wurden Hunde und Katzen mit pulmonalen Rundherden aufgenommen, an denen zunächst eine klassische Röntgenuntersuchung und anschließend innerhalb von 14 Tagen eine computertomographische Untersuchung (CT) durchgeführt wurde. Neben der Darstellung möglicher Limitationen der klassischen Röntgenuntersuchung wurde auch deren Sensitivität hinsichtlich des Vorliegens pulmonaler Rundherde im Vergleich zur CT als Goldstandard untersucht. Gemäß den Einschlusskriterien wurden 50 Hunde und 20 Katzen in die erste Studie aufgenommen. Die zweite Untersuchung beschäftigt sich mit der Sensitivität eines computerassistierten Detektionssystems sowie dessen möglichen Mehrgewinns für den Radiologen bei der Detektion pulmonaler Rundherde in der Tiermedizin. Darüber hinaus wurden die möglichen Limitationen eines solchen Systems untersucht. In die Untersuchung wurden nicht nur Tiere mit Rundherden eingeschlossen, sondern auch solche mit Massen (Herde größer 3 cm). Ausgeschlossen waren Patienten mit mehr als 50 Rundherden pro Lungenhälfte sowie Rundherde/Massen, die vollständig in Atelektasen eingebettet waren. Gemäß den Einschlusskriterien wurden bei 51 Hunden und 16 Katzen insgesamt 586 Rundherde als Referenzwert für die CAD zugrunde gelegt. Ergebnisse: Als ein Ergebnis aus der vorliegenden ersten Studie zeigt sich für die Projektionsradiographie eine Detektionsrate von insgesamt 61 % (64 % für Hunde und 55 % für Katzen) verglichen mit der CT als Goldstandard. Gründe für eine fehlende Detektion liegen vor allem darin, dass die Röntgenuntersuchung im Ergebnis ein Summationsbild liefert. Daneben spielt auch die Rundherdgröße eine (untergeordnete) Rolle. Das in der zweiten Studie eingesetzte Detektionssystem zur computerassistierten Detektion pulmonaler Rundherde wies für die Tiermedizin eine Sensitivität von 69,4 % auf. Gleichzeitig wurde eine hohe Anzahl falsch positiver sowie falsch negativer Befunde durch die CAD verzeichnet. Dennoch ließ sich durch den Einsatz der CAD die Sensitivität von Untersucher 1 von 89,2 % auf 94,7 % steigern, die von Untersucher 2 von 87,4 % auf 90,8 %. Schlussfolgerungen: Aufgrund der engen Einschlusskriterien dieser Studie kann für die Detektion pulmonaler Rundherde in der Projektionsradiographie als Mindestwert die hier ermittelte durchschnittliche Sensitivität von 61 % zugrunde gelegt werden. Die klassische Röntgenuntersuchung eignet sich weiterhin als erstes bildgebendes Verfahren für die pulmonale Rundherddetektion, für ein genaues Staging sollte allerdings die CT angewandt werden. Für eine fehlende Rundherddetektion war nicht primär die geringe Größe der Rundherde ursächlich, sondern vielmehr Begleiterkrankungen, die mit einer Transparenzminderung der Lunge einhergingen. Daher sollte insbesondere dann die CT zum Einsatz kommen, wenn zusätzliche Veränderungen wie beispielsweise ein Pleuraerguss vorliegen. Für die Detektion pulmonaler Rundherde in der CT-Untersuchung gilt, dass die Sensitivität des Radiologen grundsätzlich durch ein automatisches Detektionssystem gesteigert werden kann. Somit eignet es sich insbesondere dann, wenn kein zweiter radiologischer Befunder vorhanden ist. Allerdings weist die CAD eine sehr hohe Anzahl falsch positiver sowie einige falsch negative Befunde auf, so dass sich für ihren routinemäßigen Einsatz in der Tiermedizin derzeit noch Limitationen ergeben.:Inhaltsverzeichnis 1 EINLEITUNG 1 2 LITERATURÜBERSICHT 3 2.1 Neoplasien der Lunge bei Hund und Katze 3 2.2 Bildgebende Diagnostik bei pulmonalen Neoplasien 7 2.2.1 Definition des pulmonalen Rundherdes 13 2.2.2 Detektion von pulmonalen Rundherden in der Projektionsradiographie 15 2.2.3 Detektion von pulmonalen Rundherden in der CT-Untersuchung 17 2.2.4 Stellenwert der computerassistierten Detektion zur Erkennung pulmonaler Rundherde 18 3 PUBLIKATIONEN 20 3.1 Vergleich von Projektionsradiographie und Computertomographie zur Detektion pulmonaler Rundherde bei Hund und Katze 20 3.2 CT-Untersuchungen zur computerassistierten Detektion von pulmonalen Rundherden bei Hund und Katze 28 4 DISKUSSION 36 4.1 Diskussion der Methodik 36 4.2 Diskussion der Ergebnisse 45 5 ZUSAMMENFASSUNG 50 6 SUMMARY 52 7 LITERATURVERZEICHNIS 54 / Introduction: The early detection of pulmonary nodules plays a key role in neoplastic conditions of dogs and cats substantially influencing prognosis and therapy options. The aim of our first study was to outline the actual diagnostic value as well as the potential limitations of projection radiography for detection of pulmonary nodules. Our second study addresses the newer aspect of computer assisted detection (CAD) and its possible application in veterinary medicine. Materials and methods: The investigation period was between 2005 and 2011. In our first study we included those dogs and cats with pulmonary nodules that underwent a radiographic examination as well as a computed tomographic examination (CT) within a period of 14 days. Aside from the description of possible limitations of projection radiography, we also evaluated its sensitivity for detection of pulmonary nodules compared to CT as gold standard. According to the inclusion criteria 50 dogs and 20 cats were admitted to this study. The second study dealt with the sensitivity of a computer assisted detection system and its potential benefit for radiologists for the detection of pulmonary nodules in veterinary medicine. Furthermore, we outlined possible limitations of the detection system. This study not only comprised dogs and cats with pulmonary nodules, but also those with pulmonary masses (i.e. nodules > 3 cm). We excluded patients with more than 50 nodules either in the right or the left lung as well as nodules/masses embedded in a massive atelectasis. According to our inclusion criteria, we determined 586 nodules in total, distributed on 51 dogs and 16 cats used as reference value for the CAD. Results: As one result of our first study, we found a detection rate of 61 % (64 % for dogs and 55 % for cats) for projection radiography in comparison to CT as gold standard. Reasons for a missing detection of pulmonary nodules are predominantly limitations that come along with superimpositions using projection radiography; apart from that, nodule size is of some subsidiary meaning. The detection system for the computer assisted detection of pulmonary nodules used in the second study showed a sensitivity of 69.4 % in veterinary medicine. Additionally a high number of false positive findings as well as false negative findings was detected by CAD. However, due to the use of CAD the sensitivity of examiner 1 increased from 89.2 % to 94.7 %, the sensitivity of examiner 2 increased from 87.4 % to 90.8 %. Conclusions: Based on the strict inclusion criterion in this study the average sensitivity of 61 % can be used as a minimum for the detection of pulmonary nodules using radiographs. Projection radiography is suitable as first line diagnostic tool for the detection of pulmonary nodules. For accurate tumor staging CT should be used. Since predominant reasons for a missing detection of pulmonary nodules consisted of limitations that come along with superimpositions (like pleural effusion) CT is especially recommended in those cases. In general, the sensitivity of radiologists can be improved by an automatic detection system concerning the detection of pulmonary nodules using CT. Especially in those cases, when no second reader is available, CAD is suitable. However, the CAD system we used herein yielded a high number of false positive findings as well as false negative findings; therefore, its use in veterinary medicine on a routine basis still has some limitations.:Inhaltsverzeichnis 1 EINLEITUNG 1 2 LITERATURÜBERSICHT 3 2.1 Neoplasien der Lunge bei Hund und Katze 3 2.2 Bildgebende Diagnostik bei pulmonalen Neoplasien 7 2.2.1 Definition des pulmonalen Rundherdes 13 2.2.2 Detektion von pulmonalen Rundherden in der Projektionsradiographie 15 2.2.3 Detektion von pulmonalen Rundherden in der CT-Untersuchung 17 2.2.4 Stellenwert der computerassistierten Detektion zur Erkennung pulmonaler Rundherde 18 3 PUBLIKATIONEN 20 3.1 Vergleich von Projektionsradiographie und Computertomographie zur Detektion pulmonaler Rundherde bei Hund und Katze 20 3.2 CT-Untersuchungen zur computerassistierten Detektion von pulmonalen Rundherden bei Hund und Katze 28 4 DISKUSSION 36 4.1 Diskussion der Methodik 36 4.2 Diskussion der Ergebnisse 45 5 ZUSAMMENFASSUNG 50 6 SUMMARY 52 7 LITERATURVERZEICHNIS 54

Ultrasound imaging is one of the fundamental examinations of thyroid nodules, determining whether a patient undergoes a cytological examination, which is essential for the decision on a possible thyroid surgery. Unfortunately, the cytological examination has limited specificity and potential surgery carries risks. Therefore, other diagnostic methods are being sought with hope that they will be able to bring more certainty into diagnostics. One of the new methods is computer-aided diagnosis (CAD), which exhibits promising results using image analysis and machine learning. In this study, we present two somewhat similar, yet different, CAD approaches. The first approach is based on analysing entire nodules using a Segmentation Based Fractal Texture Analysis (SFTA) algorithm that splits the image into individual grayscale bands. Using this approach, we have achieved an accuracy of 92.4% using random forests (RF) and 95% using support vector machines (SVM) on a data set of 40 images evaluated by the cross-validation method. The second CAD approach is also based on the method of multiple image thresholding, but the difference is, that a larger number of predictors describing the binary texture are extracted from the individual grayscale bands. Furthermore, the analysis did not take place on whole nodules, but on...

Nitrogen-fixing bacteria in soybean nodules convert atmospheric nitrogen to plant-available forms in exchange for carbon from the plant, but other non-nitrogen-fixing bacteria also reside in nodules, and their role in the nodule is not well understood. This study was conducted to determine the effect of three non-nitrogen-fixing Pseudomonas spp. strains isolated from nodules on soybean, and we hypothesized these strains benefit soybean. A greenhouse study in which two cultivars of soybean (Asgrow AG46X6 and Pioneer P48A60X) were treated with three fluorescent Pseudomonas spp. strains (referred to in this study as Bullseye, Pancake, and Starfish) and an uninoculated control. Soybeans were harvested at two time points: the R2/R3 growth stage and the R6 growth stage. Following each harvest, measures of growth, yield, and nitrogen fixation were taken, and data were analyzed using two non-parametric, multivariate analyses: multiple response permutation procedure (MRPP) and permutational multivariate analysis of variance (PERMANOVA). Both analyses showed soybeans of both cultivars treated with Pancake differed from controls following the first harvest but not the second. When analyzed individually, most metrics for growth, yield, and nitrogen fixation following the first harvest were not significantly different between Pancake and control treatments, but Pancake treatment means were still generally higher than controls. If metrics are considered collectively in conjunction with the results of the multivariate analyses, the results show Pancake generally increased soybean growth and nitrogen fixation. These findings support the hypothesis that non-nitrogen-fixing bacteria from nodules benefit plants, and such bacteria have the potential to serve as biofertilizers. / Master of Science in Life Sciences / Soybeans are one of the most commonly grown crops in the world, and nitrogen-fixing bacteria colonize the roots of soybeans and initiate the formation of spherical nodules attached to the roots. Inside the nodules, these bacteria convert atmospheric nitrogen to plant-available forms in exchange for sugar from the plant, and such bacteria reduce the need to add nitrogen fertilizer to agricultural fields. Other non-nitrogen-fixing bacteria also reside in nodules, but their role in the nodule is not well understood. If these bacteria benefit soybeans, they have the potential to serve as biofertilizers (microbial inoculants that promote plant growth). This study was conducted to determine whether non-nitrogen-fixing bacteria isolated from nodules benefit soybean. A greenhouse study in which two cultivars of soybean (Asgrow AG46X6 and Pioneer P48A60X) were grown in soil and were either left uninoculated or were inoculated with one of three strains of bacteria from the genus, Pseudomonas (referred to in this study as Bullseye, Pancake, and Starfish). Following harvest, measures of growth, yield, and nitrogen fixation were taken, and data showed the bacteria generally benefited the soybean plants. Although, these results showed the bacteria benefitted the plants, field trials and further testing in the greenhouse should be conducted before using these bacteria as commercial biofertilizers. Additionally, the effects of other non-nitrogen-fixing nodule bacteria on soybeans should also be tested to identify other beneficial strains, and the cost of production should be compared to the potential gains of using such bacteria before they are developed into biofertilizers.

Les légumineuses sont connues pour leurs capacités à établir une relation symbiotique avec des bactéries du sol fixatrices de l'azote atmosphérique. Cette interaction aboutit à la formation d'un nouvel organe au niveau des racines, la nodosité, au sein duquel le symbiote convertit l'azote atmosphérique (N2) en ammoniac, qui peut être directement consommé par les plantes. A l’intérieur de cette nodosité, la concentration en oxygène (O2) est maintenue à un très faible niveau car la réaction de réduction du N2 par l’enzyme bactérienne nitrogénase est inhibée par des traces d’oxygène. Un mécanisme de perception directe de l'O2 impliquant des membres de la famille des facteurs de transcription « Ethylene Responsive Factors » (ERFs) du groupe VII a récemment été découvert chez Arabidopsis thaliana. Ces facteurs de transcription (FT) possèdent une extrémité N-terminale caractéristique avec un résidu de cystéine à la seconde position. Dans des conditions normales d'O2, les FT sont conduit à la dégradation suivant une voie spécifique du protéasome. En condition de stress hypoxique, les TFs sont stabilisés et peuvent activer l’expression des gènes de réponse à l'hypoxie. Il a été démontré que la présence d’O2 et de NO était nécessaire pour déstabiliser ces protéines, et qu'une réduction de la disponibilité de l'un ou l'autre des gaz est suffisante pour protéger le résidu cystéine N-terminale de l'oxydation. L’objectif de cette thèse a été d'étudier le rôle de la famille ERF-VII dans la perception et l'adaptation au manque d'O2 chez M. truncatula. Des travaux ont aussi été menés pour déterminer l’importance du NO dans le fonctionnement en microoxie de la nodosité. Quatre gènes codant pour des facteurs de transcription de la famille ERF-VII ont été identifiés dans le génome de M. truncatula. La caractérisation de cette famille au niveau transcriptionnel a révélé que seul MtERF-B2.2 était induit par le stress hypoxique et au cours du développement des nodosités. Les trois autres, MtERF-B1.1, MtERF-B1.11 et MtERF-B2.3, sont constitutivement exprimés dans les feuilles, les racines et les nodosités. Pour étudier la stabilité de la protéine MtERF-B2.1, l’orthologue de RAP2.12 principal ERF-VII décrit dans la perception de l’O2 chez Arabidopsis, en fonction de la disponibilité de O2/NO, nous avons réalisé une protéine de fusion entre l’extrémité N-terminale de notre protéine et la protéine rapporteur luciférase. Les résultats obtenus sur des protoplastes d'Arabidopsis montrent l’implication la partie N-terminale de MtERF-B2.1 dans la régulation de la stabilité de la protéine, mais en contradiction avec les résultats obtenus en plantes composites de M. truncatula. La fonction de MtERF-B2.1 et MtERF-B2.11 a également été étudiée dans le cadre de la réponse au stress hypoxique et au cours du processus de nodulation en utilisant une stratégie d'interférence ARN. Des racines transgéniques dérégulées sur l’expression de MtERF-B2.1 et MtERF-B2.11 ont montré un défaut d’activation de plusieurs gènes de réponses à l'hypoxie tels que l’alcool déshydrogénase (ADH1) ou la pyruvate décarboxylase (PDC1). Ces racines transgéniques ARNi-MtERF-B2.1/B2.11 sont également affectées dans l'interaction symbiotique avec une réduction significative de la capacité de nodulation et de l'activité de fixation de l'azote dans les nodules matures. En conclusion, ces travaux révèlent que le mécanisme de détection d'O2 est médié par les ERF-VII dans les nodosités de M. truncatula et que ce mécanisme, associé aux cibles moléculaires régulées en aval, participe au développement de cet organe et au maintien de la capacité de fixatrice de celui-ci. De plus, les résultats indiquent que MtERF-B2.1/B2.11 sont des régulateurs positifs du métabolisme anaérobie et que les gènes associés au cycle hémoglobine-NO sont susceptibles d'activer d'autres voies de génération d'ATP. / Legume crops are known for their capacities to establish a symbiotic relationship with nitrogen fixing soil bacteria. This mutualism culminates in the formation of a new plant organ, the root nodule, in which the symbiont converts atmospheric nitrogen (N2) into ammonia, which can be directly consumed by plants. In nodules, bacterial nitrogenase enzyme is inhibited by traces of oxygen (O2) so different mechanisms maintain this organ at low O2 level. At the same time, nodules need to maintain a high ATP level to support the nitrogenase activity, which is highly energy demanding. Thus, a balance between a tight protection from O2 and an efficient energy production, referred as the “O2 paradox” of N2-fixing legume nodules, has to be reached. In Arabidopsis thaliana, a direct oxygen sensing mechanism has recently been discovered involving members of the ethylene responsive factors (ERFs) group VII. These transcription factors (TFs) possess a characteristic N-terminal amino acid with a cysteine residue at the second position that, under normal O2 conditions, leads to protein degradation following a specific pathway called the N-end rule pathway. Furthermore, it was shown that both O2 and nitric oxide (NO) are required to destabilize the ERFs VII and that a reduction in the availability of either gas is sufficient to stabilize these proteins. Therefore, the goal of this thesis was to investigated the role of ERF-VII family in O2 sensing and adaptation to hypoxia in M. truncatula, model plant for legumes, and to understand how NO interacts with O2 in hypoxic signalization in the microoxic environment that characterizes the nodule. We identified four genes belonging to the ERF-VII TF family in the M. truncatula genome, which present a strong similarity with ERF-VII of Arabidopsis. The characterization of this family at the transcriptional level revealed that only MtERF-B2.2 is up-regulated by hypoxia stress and during nodule development. The three others, MtERF-B1.1, MtERF-B1.11 and MtERF-B2.3 are found constitutively expressed in leaves, roots and nodules. To investigated the protein stability of MtERF-B2.1, the closest orthologous to AtRAP2.12 described as O2-sensors in Arabidopsis, in function of O2/NO availability, we realized a fusion protein with the luciferase reporter protein. Our results on Arabidopsis protoplasts indicated that the N-terminal part of MtERF-B2.1 drives its O2-dependent degradation by the N-end rule pathway. The function of MtERF-B2.1 and MtERF-B2.11 was also investigated both in response to hypoxia stress and during the nodulation process using an RNA interference strategy. Silencing of MtERFB2.1 and MtERF-2.11 showed a significant lower activation of several core hypoxia-responsive genes such as ADH1, PDC1, nsHb1 and AlaAT. These double knock-down transgenic roots were also affected in symbiotic interaction with a significant reduction of the nodulation capacity and nitrogen fixation activity in mature nodules. Overall, the results reveal that O2 sensing mechanism is mediated by ERF-VIIs in M. truncatula roots and nodules and that this mechanism, together with downstream targets, is involved in the organ development and ability to efficiently fix nitrogen. Furthermore, results indicated that MtERF-B2.1/B2.11 are positive regulator of the anaerobic metabolism and the Hb-NO cycle– related genes likely in order to activate alternative ATP generation pathways.

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A series of glasshouse and laboratory experiments was carried out to enable comparison of two woody perennial legumes, gorse and broom, with other legumes, nodulated non-legumes and other biological nitrogen fixing systems. Both species had distinct juvenile phases in which broom closely resembled herbaceous species in appearance, but adult plants of both species bore little resemblance to each other or to other legume species. Nodule development was similar to that of other legumes, but mature nodules exhibited structural adaptations to longevity - meristematic activity, a well developed vascular system and numerous cytoplasmic granules in cortical cells. Acetylene reduction and ¹⁵N₂ fixation continued for much longer following excision than has been observed in other legumes. In all experiments, broom nodules exhibited higher rates of acetylene reduction and nitrogen fixation than did gorse nodules. The first detectable product of nitrogen fixation in excised nodules - ammonia - was rapidly incorporated into amide and ∝ amino groups and another unidentified fraction. The principle free amino acid in nodules and sap was asparagine. Its preponderance increased as plants aged. Whole nodulated plants and excised nodules of both species exhibited a relatively low temperature optimum for growth and nitrogen fixation (22°C). They were very sensitive to elevated temperatures. Results indicated that gorse and broom have relatively low light requirements. When aeration was sufficient, combined nitrogen had little effect on growth of nodulated plants. Nodulation in both species was reduced by increasing amounts of combined nitrogen. High levels (100 mg/1) of nitrate and ammonia caused considerable inhibition of nitrogen function. Both species showed large responses to phosphate, but were able to grow and fix nitrogen when supplied with low amounts of phosphate. Boron deficiency reduced nitrogen fixation. Nodulation was increased to compensate for this. Considerable amounts of nitrogen can be contributed to the ecosystem in gorse end broom litter. Direct transfer between gorse or broom and Pinus radiate is likely to be small and may be masked by competition for other nutrients. These findings are discussed with respect to the use of gorse and broom to overcome nitrogen deficiency in reafforestation on the Moutere Gravels, in Nelson, N.Z.

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Red alder (Alnus rubra Bong.) is the only tree in British Columbia and the Northwest US to engage in actinorhizal symbiosis to fix atmospheric nitrogen. This study was conducted to explore the plasticity in growth and physiology among 58 17-year-old red alder families in response to variation in climate in two common garden plots, one at Bowser, BC and one at Terrace, BC. Physiological assessments included height and diameter growth, bud flush, water use efficiency as measured by δ13C, cold hardiness as measured by controlled freezing and electrolyte leakage, autumn leaf senescence, and instantaneous and seasonally integrated rates of nitrogen fixation as measured by acetylene reduction and natural abundance δ15N isotope analysis, respectively. Significant differences were identified among families for growth (height and diameter), bud burst stage, leaf senescence, cold hardiness, and bud nitrogen content. No significant differences among families were identified for water use efficiency as measured by δ13C, or for rates of nitrogen fixation as measured by either acetylene reduction or natural abundance δ15N. This study identified possible adaptive differences among red alder genotypes, especially in traits such as bud flush timing, cold hardiness, or nitrogen fixation and their respective contributions to growth. These differences often reflected a tradeoff between growth and the ability to tolerate an extreme environment. Cold hardiness results indicate that red alder families are well adapted to their climate of origin, and may not be able to acclimate sufficiently to a northward assisted migration of genotypes. Nitrogen fixation results demonstrated gaps in our current knowledge of Frankia distribution and impact on the actinorhizal symbiosis in British Columbia. / Graduate

La fixation symbiotique d’N par les légumineuses est très sensible aux ravageurs, provoquant des dommages sur les racines nodulées, avec un impact sur la fixation d’N et la croissance qui demeure mal connu. Nous avons alors analysé la réponse adaptative de la fixation symbiotique et de la croissance du pois Frisson sauvage et 3 de ses mutants hypernodulants P64, P118 et P121, respectivement mutés sur les gènes SYM28, SYM29 et NOD3, à une ablation de la moitié du système racinaire, en fin de phase végétative. La réponse adaptative a été mesurée 8 jours après ablation, dans des conditions d'alimentation en carbone par la photosynthèse variées. A 380 ppm, le mutant P118 a montré la plus faible diminution de l’activité spécifique de fixation (-17%) suite à l’ablation comparé au sauvage et aux 2 autres mutants (-36% à -62%) associé à une accélération chez les mutants P118 et P121 et un maintien (sauvage et P64) de la croissance des nodosités. A 150 ppm, suite à l’ablation, l’activité spécifique de fixation symbiotique par les nodosités a été diminuée (sauvage), maintenue (P64 et P118) ou augmentée (P121), associée à une accélération (sauvage et P121) ou un maintien (P64 et P118) de la croissance des nodosités. A 750 ppm, l’activité spécifique de fixation a diminué suite à l’ablation pour tous les génotypes, associée à un ralentissement (P64), un maintien (P118, sauvage) ou une faible accélération (P121) de la croissance des nodosités. Les résultats montrent une plus grande capacité de la fixation symbiotique des mutants hypernodulants (P118 et P121 essentiellement) à résister au stress provoqué par l’ablation. / Symbiotic N fixation of legumes is very sensitive to environmental stresses, like pea pests damaging nodulated roots. However, the impact on their N uptake capacity and plant growth has not been studied so far.We analyzed the adaptive response symbiotic N2 fixation and plant growth of pea wild type Frisson and hypernodulating mutants P64, P118 and P121 mutated respectively on genes SYM28, SYM29 and NOD3 to root pruning of half the root system at the end of the vegetative stage. The adaptive responses of pea: cv. Frisson and 3 of its hypernodulating mutants were compared under varying carbon supplies from photosynthesis.At 380 ppm, mutant P118 showed the lowest decrease of the specific activity of N fixation (-17%) following root pruning compared to the wild type and the 2 others mutants (-36% to -62%), associated to an acceleration (P118 and P121) and a maintained (wild type and P64) nodule growth. At 150 ppm, following root pruning, specific activity of N fixation of nodules decreased in wild type, was maintained in P64 and P118 and increased in P121. At 750 ppm, specific activity of N fixation of nodules decreased for all genotypes following root pruning, associated to a maintained nodule growth in wild type and P118, a slower growth in P64 and acceleration in P121.Our results showed a greater capacity of hypernodulating mutants P118 and P121 to withstand the stress induced by root pruning of half the root system.