Whitebark pine (Pinus albicaulis) is a foundation and keystone species at alpine treelines of the northern Rocky Mountains and is threatened by the fungus white pine blister rust (Cronartium ribicola). This disease affects all five-needled white pines, but has caused particularly widespread mortality in whitebark pine. Objectives of this research were: 1) to characterize the landscape structure of the treeline study sites at Divide Mountain in Glacier National Park and at Wyoming Creek in the Beartooth Mountains of Montana using landscape metrics and fieldwork; 2) to determine the frequency of blister rust infection of whitebark pine trees and determine if landscape pattern is correlated with higher infection rates; and 3) to characterize the climate at alpine treeline. I used both field surveys and subsequent statistical analysis to meet these objectives. Field data collection included detailed surveys of blister rust infection of treeline whitebark pine and characterization of landscape cover type in a combined total of 60 quadrats, positioned at the study sites using a random sampling scheme stratified by aspect. Landscape analysis of metrics such as patch area, proximity and contagion were generated in FRAGSTATS software and ArcGIS. Spearman's rank correlation analysis found significant correlations between tree island patch size, patch perimeter, and percent of landscape and blister rust infection intensity at both study sites. These findings support previous research involving the relationship between patch area and blister rust infection rates and contribute to the field of landscape ecology by understanding what other landscape metrics are significant in invasive disease infection patterns. / Master of Science

The complex interactions at the interfaces of minerals, microbes, and metals drive the cycling of iron and the fate and transport of metal(loid)s in contaminated systems. The former uranium mine near Ronneburg, Germany is one such system, where slightly acidic mine drainage crossing a steep redox gradient (groundwater outflow into a stream) forms and transforms iron (oxy)hydroxide nanoparticles. These particles interact with toxic metal(loid)s in water and sediments. Iron oxidizing and reducing bacteria also play a role in these processes. Biogeochemical reactions are influenced by nanoscale properties, and thus it is critical to probe environmental samples with appropriate techniques such as analytical transmission electron microscopy (TEM). This dissertation presents two studies on the iron (oxy)hydroxide mineral nanoparticles found in the Ronneburg mine drainage system. The first study uses TEM in conjunction with bulk analytical techniques to demonstrate the complexity of iron (oxy)hydroxide transformations at the steep redox gradient, and the partitioning of metal(loid)s within those mineral phases. An important result was the identification of Zn-bearing green rust platelets in the anoxic outflow water. Green rust minerals have only been identified in nature a handful of times, and we believe this work to be only the second to examine naturally occurring green rust using high resolution TEM (HR-TEM). Downstream of the outflow, aggregates of poorly crystalline iron oxide spheroids co-precipitated with amorphous silica formed and settled to the stream bed, where they aged to form nanoparticulate goethite and sequestered metals such as As and Zn. However, significant concentrations of Zn and Ni remained in the dissolved/nano (< 0.1 um) water fraction and continued downstream. The second study demonstrates that natural green rust nanoparticles and their synthetic analogs can be complex polycrystalline phases composed of crystallites only a few nanometers in size, and often include nano-regions of amorphous material. In addition to the typical pseudo-hexagonal platelet morphology, green rust nanorods were synthesized, which has not previously been reported. This work has important implications for the reactivity of green rust with biogeochemical interfaces in natural, anthropogenic, and industrial systems. A third study, presented in the appendix, characterizes the bacterial community at the Ronneburg mine drainage site and highlights iron oxidizers such as Gallionella sp., in particular those that form stalks of iron oxide nanoparticles. These biogenic stalks also contribute to the uptake of metal contaminants in water and sediments. The science of iron cycling is complex. It requires field-based exploration to enrich the contributions made by experimental, laboratory and modeling studies. This dissertation adds another chapter in the search for filling in missing pieces of this interconnected system. / Ph. D.

Reducing apple (Malus x domestica Borkh.) crop load during bloom is a reliable option for increasing fruit quality and return bloom. In this thesis, multiple approaches to improving bloom thinning practices are discussed. The first project analyzed the pollen tube growth of several crabapple cultivars. Previous research had improved the use of bloom thinning chemicals, by coordinating the application timing with the pollen tube growth between pollination and fertilization. However, pollen tube growth rates have only been measured in a few genotypes. In Chapter 2, the pollen tube growth rates of five crabapple cultivars were measured in the styles of 'Fuji', 'Golden Delicious', and 'Pink Lady' flowers, at four temperatures 12, 18, 24 and 30 C. Complex relationships were found among paternal pollen tube growth, maternal cultivar, and temperature. Chapters 3 and 4 describe projects where organically-approved chemicals, including the biofungicide, Regalia, were evaluated for their ability to simultaneously reduce crop load and decrease early season disease infection. These chemicals were applied in conventionally managed orchards (Chapter 3), and in an organically-managed 'Honeycrisp' orchard (Chapter 4). The number of chemicals approved for bloom thinning is limited, especially in the Eastern U.S. where lime sulfur and oil applications are not permitted during bloom. These studies indicate Regalia, applied during bloom, can reduce crop load and provide early season disease control. The research presented in this thesis provides new knowledge that can be incorporated into crop load management practices in both conventional and organic apple orchards. / Master of Science

Leaf rust and stripe rust of wheat (Triticum aestivum L.) are caused by the fungal pathogens Puccinia triticina, and Puccinia striiformis f.sp. tritici, respectively. In North America, the incorporation of adult-plant resistance (APR) genes into breeding lines has been an important strategy to achieve durable resistance to both diseases. Previously, the spring wheat cultivar AC Domain was reported to express an effective level of adult-plant resistance (APR) to leaf rust under field conditions. Early gene postulation work had suggested AC Domain might carry the APR gene Lr34 due to its phenotypic similarity to other Lr34 carrying lines. However, new gene specific markers have shown that AC Domain is not a carrier of Lr34. The objective of this research was to genetically localize the resistance in AC Domain, which is important because the cultivar has frequently been used as a parent in Canadian breeding programs, primarily for its value as a source of pre-harvest sprouting resistance. A mapping population of 185 doubled haploid (DH) lines derived from the cross ‘RL4452’ by ‘AC Domain’ was used for this study. RL4452 is a known carrier of Lr34. During 2011-2012, the DH population was evaluated in field leaf rust nurseries at Saskatoon, SK and Portage, MB and at a stripe rust nursery at Lethbridge, AB. Field results indicated that rust resistance in the mapping population was variable, with lines ranging from highly resistant, to highly susceptible. DH lines carrying Lr34 showed a high level of resistance to both diseases. Thus, the non-Lr34 carriers were genotyped using select SSR markers, and by an Illumina 9k Infinium iSelect SNP assay for subsequent quantitative trait loci (QTL) analysis. QTL analysis revealed that AC Domain donated a major resistance QTL located on chromosome 2BS, that mapped 46 cM proximal to markers linked to Lr16, and explained a significant portion of the leaf and stripe rust phenotypic variance in all test environments. In addition, this QTL was significantly associated with the expression leaf tip necrosis (LTN), reduction in area under the disease progress curve (AUDPC), and coefficient of infection (CI). In certain environments the interaction between the 2B QTL and Lr34 was additive resulting in a superior level of rust resistance. Indoor rust testing showed AC Domain was susceptible to both diseases at the seedling stage. Taken together these results suggest that the identified resistance in AC Domain is likely due to the presence of an APR gene, on chromosome 2BS.

This thesis presents three different approaches to model corrosion-induced crack propagation in reinforced concrete structures. The first approach is solved numerically using finite differences to model the softening behaviour of concrete in tension. The second approach idealizes the concrete cover as either a brittle elastic or an elastoplastic material so that it may be solved using a closed-form solution. Both approaches are based on a thick-walled cylinder (TWC) analogy and consider rust compressibility and rust diffusion into cracks. The third approach uses finite element modelling to validate the application of the TWC and perform a parametric study. The results obtained using each approach are compared against each other as well as against experimental results. The TWC was found to be an appropriate analogy for the geometries and reinforcement configurations considered. Analytical models were found to provide upper and lower limits to the results based on the numerical model. The experimental data found in the literature showed reasonable agreement with predictions from the numerical and elastoplastic models.

This thesis aims to provide recommendations for interfacing two memory-safe programming languages, Rust and SPARK. The comparison of Rust and C/C++, as well as SPARK and C/C++, has been thoroughly researched. However, this level of investigation hasn’t been as extensive between memory-safe languages. SPARK is a subset of Ada, a programming language with a long track record in safety-critical applications. Rust is a multi-paradigm language that has gained popularity since its emergence roughly a decade ago. Both languages implement ownership systems and type safety, which are instrumental in developing safe and reliable software. Memory-safety bugs in code written in C/C++ account for about 70 % of major vulnerabilities in the industry, as reported by organizations such as Microsoft, Apple, and Google. While tools to avoid memory errors exist, code cannot be made safe retroactively, which creates a need for languages designed with safety in mind, such as Rust and SPARK. Combining those two languages is a very promising path for low-level and systems programming and safety-critical applications (automotive, avionics, medical etc.). This thesis identifies best practices for safe bindings between Rust and SPARK, focusing on ensuring memory safety, type safety, and ownership, and then analyzes how to maintain or transfer those properties. The thesis provides clear recommendations based on control study programs and a real-world example using BBQueue, a circular buffer library suitable for embedded systems implemented in both languages. The identified best practices can be used for safe bindings and automated tools/code generation. This thesis fills a gap in existing research, primarily focusing on combining safe and unsafe languages. It provides a valuable contribution to software security and safety-critical systems. / Denna avhandling syftar till att ge rekommendationer för att koppla samman två minnessäkra programmeringsspråk, Rust och SPARK. Sådana kombinationer har redan studerats utförligt mellan Rust/SPARK och de osäkra språken C/C++, men det finns relativt lite information och forskning angående minnessäkra språk. SPARK är en delmängd av Ada, ett språk som har använts i decenier i säkerhetskritiska applikationer. Rust är ett multiparadigmatiskt språk som har blivit populärt sedan dess skapande för ungefär ett decennium sedan. Båda språken implementerar ägarskapssystem och typsäkerhet, vilka är avgörande för att utveckla säkra och tillförlitliga programvaror. Minnesfel i C/C++ står för cirka 70 procent av de stora sårbarheterna i branschen, som rapporterats av organisationer såsom Microsoft, Apple och Google. Även om det finns verktyg för att undvika minnesfel kan koden inte göras säker retroaktivt, vilket skapar ett behov av språk som är designade med säkerhet i åtanke. Att kombinera Rust och SPARK är en mycket lovande väg för systemprogrammering, låg nivå och säkerhetskritiska applikationer (bilindustri, flygavionik, medicinskt etc). Denna avhandling identifierar bästa praxis för säkra bindningar mellan Rust och SPARK, med fokus på att säkerställa minnessäkerhet, typsäkerhet och ägarskap, och analyserar sedan hur man kan behålla eller överföra dessa egenskaper. Avhandlingen ger klara rekommendationer baserade på kontrollstudieprogram och ett exempel med hjälp av BBQueue, ett cirkulärt buffertbibliotek som används i inbyggda system. Dessa resulat kan användas för att skapa säkra bindningar, manuelt eller med ett automatiserat verktyg. Denna avhandling fyller en lucka i befintlig forskning, som främst fokuserar på att kombinera säkra och osäkra språk. Den bidrar värdefullt till programvarusäkerhet och säkerhetskritiska system.

With the current developments in modern web browsers, WebAssembly has been a rising trend over the last four years. Aimed at replacing bits of JavaScript functionality, it attempts to bring extra features to achieve portability and sandboxing through virtualisation. After the release of the WebAssembly System Interface, more and more projects have been working on using it outside web pages and browsers, in scenarios such as embedded, serverless, or distributed computing. This is thus not only relevant to the web and its clients, but also to applications in distributed systems. Considering the novelty of the topic, there is currently very little related scientific literature. With constant changes in development, proposals and goals, there is a large gap in relevant research. We aim to help bridge this gap by focusing on Rust and Arc-Lang, a domain-specific language for data analytics, in order to provide an overview of how far the technology has progressed, in addition to what runtimes there are and how they work. We investigate what kind of use case WebAssembly could have in the context of distributed systems, as well as how it can benefit data processing pipelines. Even though the technology is still immature at first glance, it is worth checking whether its proposals have been implemented, and how its performance compared to that of native Rust can affect data processing in a pipeline. We show this by benchmarking a filter program as part of a distributed container environment, while looking at different WebAssembly compilers such as Cranelift and LLVM. Then, we compare the resulting statistics to native Rust and present a synopsis of the state of WebAssembly in a distributed context. / I takt med den nuvarande utvecklingen av moderna webbläsare har WebAssembly stigit i trend under de senaste fyra åren. WebAssembly har som syfte att ersätta och utöka JavaScript med funktionalitet som är portabel och isolerad från omvärlden genom virtualisering. Efter lanseringen av WebAssembly System Interface har fler och fler projekt börjat applicera WebAssembly utanför webbsidor och webbläsare, i scenarier som inbäddade, serverlösa eller distribuerade beräkningar. Detta har gjort WebAssembly till ett språk som inte bara är relevant för webben och dess användare, utan även för applikationer i distribuerade system. Med tanke på ämnets framkant finns det för närvarande väldigt lite relaterad vetenskaplig litteratur. Ständiga förändringar i utveckling, förslag och mål har resulterat i stort gap i relevant forskning. Vi strävar efter att hjälpa till att överbrygga denna klyfta genom att studera WebAssembly i perspektivet av Rust och Arc-Lang, ett domänspecifikt språk för dataanalys, för att ge en översikt över hur långt tekniken har kommit, och samt utreda vilka exekveringssystem som finns och hur de fungerar. Vi undersöker vilken typ av användning WebAssembly kan ha i samband med distribuerade system, samt hur det kan gynna databehandlingspipelines. Även om tekniken fortfarande är ny vid första anblicken, är det värt att kontrollera om dess förslag har implementerats och hur dess prestanda gentemot Rust kan påverka databehandling i en pipeline. Vi visar detta genom att benchmarka ett filtreringsprogram som en del av en distribuerad containermiljö, samtidigt som vi tittar på olika WebAssembly-kompilatorer som exempelvis Cranelift och LLVM. Vi jämför resultaten med Rust och presenterar en sammanfattning av WebAssemblys tillstånd i sammanhanget av distribuerade system.

Doctor of Philosophy / Genetics Interdepartmental Program / Bikram S. Gill / Leaf rust, caused by fungus Puccinia triticina, is an important foliar disease of wheat worldwide. Breeding for race-nonspecific resistant cultivars is the best strategy to combat this disease. Aegilops tauschii, D genome donor of hexaploid wheat, has provided resistance to several pests and pathogens of wheat. To identify potentially new adult plant resistance (APR) genes, 371 geographically diverse Ae. tauschii accessions were evaluated in field with leaf rust (LR) composite culture of predominant races. Accessions from Afghanistan only displayed APR whereas both seedling resistance and APR were common in the Caspian Sea region. Seventeen accessions with high APR were selected for production of synthetic hexaploid wheat (SHW), using ‘TetraPrelude’ and/or ‘TetraThatcher’ as tetraploid parents. Six SHWs were produced and evaluated for APR to LR and resistance to tan spot at seedling stage. Genetic analysis and mapping of APR introgressed from accession TA2474 was investigated in recombinant inbred lines (RIL) population derived from cross between SHW, TA4161-L3 and spring wheat cultivar, ‘WL711’. Genotyping-by-sequencing approach was used to genotype the RILs. Maximum disease severity (MDS) for LR was significantly correlated among all experiments and APR to LR was highly heritable trait in this population. Nine genomic regions significantly associated with APR to LR were QLr.ksu-1AL, QLr.ksu-1BS, QLr.ksu-1BL.1, QLr.ksu-1BL.2, QLr.ksu-2DS, QLr.ksu-2DL, QLr.ksu-5AL, QLr.ksu-5DL and QLr.ksu-6BL. Association of QLr.ksu-1BL.1 with marker Xwmc44 indicated this locus could be slow-rusting APR gene, Lr46/Yr29. QTLs detected on 2DS, 2DL and 5DL were contributed by TA4161-L3 and are novel, along with QLr.ksu-5AL. Tan spot, caused by necrotrophic fungus, Pyrenophora tritici-repentis, has recently emerged as a damaging disease of wheat worldwide. To identify QTLs associated with resistance to Race 1 of P. tritici-repentis, F[subscript]2:3 population derived from cross between SHW, TA4161-L1 and winter wheat cultivar, ‘TAM105’ was used. Two major effect QTLs, QTs.ksu-1AS.1 and QTs.ksu-7AS were significantly associated with tan spot resistance and contributed by TA4161-L1. QTs.ksu-7AS is a novel QTL and explained 17% of the phenotypic variation. Novel QTLs for APR to LR and tan spot identified in SHWs add new variation for broadening the gene pool of wheat and providing resources for breeding of durable resistant cultivars.

Thesis (PhD (Agric)) -- Stellenbosch University, 2003. / ENGLISH ABSTRACT: Stripe (yellow) rust of wheat, caused by Puccinia striiformis f.sp. tritici, was first detected as a single introduction into South Africa in 1996. Two additional pathotypes have since been identified. Control of the disease may be achieved by use of genetic adult plant resistance (APR) as is present in the local cultivar 'Kariega'. The aim of this project was to understand the genetic basis of the APR in 'Kariega' to facilitate breeding of new varieties with genetic resistance to stripe rust. A partial linkage map of a 'Kariega X Avocet S' doubled haploid population covering all 21 wheat chromosomes was generated using 208 DNA markers, viz, 62 SSR, 133 AFLP, 3 RGA and 10 SRAP markers, and 4 alternative loci. The different marker techniques detected varying polymorphism, viz, overall SSR: 46%, AFLP: 7%, SRAP: 6% and RGA: 9%, and the markers produced low levels of missing data (4%) and segregation distortion (5%). A significant feature of the linkage map was the low polymorphism found in the D genome, viz, 19% of all mapped DNA markers, 11% of all AFLP markers and 30% of the total genome map distance. A region exhibiting significant segregation distortion was mapped to chromosome 4A and a seedling resistance gene for stem rust (Puccinia graminis f.sp . tritici), Sr26, mapped to chromosome 6A close to three SSR markers. The leaf tip necrosis gene, Ltn, which was also segregating in the population, mapped to chromosome 7D. Protocols for SRAP and RGA were optimised, and SRAP marker use in wheat genetic linkage studies is reported for the first time. The linkage map was used together with growth chamber and replicated field disease scores for QTL mapping. Chromosomes showing statistically significant QTL effects were then targeted with supplementary SSR markers for higher resolution mapping. The quality of disease resistance phenotypic data was confirmed by correlation analysis between the different scorers for reaction type (0.799±0.023) and for transformed percentage leaf area infected (0.942±0.007). Major QTL were consistently identified on chromosome 7D (explaining some 25-48% of the variation) and on chromosome 2B (21-46%) using transformed percentage leaf area infected and transformed reaction type scores (early and final) with interval mapping and modified interval mapping techniques. Both chromosomal regions have previously been identified in other studies and the 7D QTL is thought likely to be the previously mapped APR gene Yr 18. Minor QTL were identified on chromosomes lA and 4A with the QTL on 4A being more prominent at the early field scoring for both score types. A QTL evidently originating from 'Avocet S' was detected under growth chamber conditions but was not detected in the field, suggesting genotype-environment interaction and highlighting the need for modifications of growth chamber conditions to better simulate conditions in the field. The genetic basis of the APR to stripe rust exhibited by 'Kariega' was established by mapping of QTL controlling this trait. The linkage map constructed will be a valuable resource for future genetic studies and provides a facility for mapping other polymorphic traits in the parents of this population with a considerable saving in costs. / AFRIKAANSE OPSOMMING: Streep of geelroes van koring word veroorsaak deur Puccinia striiformis f. sp tritici, en is die eerste keer in 1996 in Suid-Afrika na introduksie van 'n enkele patotipe waargeneem. Twee verdere patotipes is sedertdien in Suid-Afrika gei"dentifiseer. Beheer van die siekte word veral moontlik gemaak deur die gebruik van genetiese volwasseplantweerstand soos gei"dentifiseer in die plaaslike kultivar 'Kariega'. Die doel van hierdie studie was om die genetiese grondslag van die streeproesweerstand te ontrafel ten einde die teling van nuwe bestande kultivars moontlik te maak. 'n Verdubbelde haplo1ede populasie uit die kruising 'Kariega X Avocet S' is aangewend om 'n gedeeltelike koppelingskaart vir die volle stel van 21 koring chromosome saam te stel. Die kaart het uit 208 DNA merkers, nl., 62 SSR, 133 AFLP, 3 RGA, 10 SRAP merkers en 4 ander lokusse bestaan. Totale polimorfisme wat deur die verskillende merkersisteme opgespoor is, was as volg: SSR: 46%, RGA: 9%, AFLP: 7% en SRAP: 6%. Die mate van ontbrekende data was gering (4%) asook die mate van segregasie distorsie (5%) van 'n enkele geval wat op chromosoom 4A gekarteer is. 'n Prominente kenmerk van die koppelingskaart is die relatiewe gebrek aan polimorfiese merkers op die D-genoom, nl., slegs 19% van alle DNA merkers en 11% van alle AFLP merkers wat slegs 30% van die totale genoom kaartafstand bestaan het. Die stamroes (Puccinia graminis f. sp. tritici) saailingweerstandsgeen, Sr26, karteer op chromosoom 6A naby drie SSR merkers. Die geen vir blaartipnekrose, Ltn, karteer op chromosoom 7D. Protokolle vir SRAP en RGA merkers is ge-optimiseer en gebruik van SRAP merkers in koppelings-analise word vir die eerste keer in koring gerapporteer. Die koppelingskaart is in kombinasie met groeikamerdata en gerepliseerde veldproefdata gebruik om die gene (QTL) vir volwasseplant streeproesweerstand te karteer. Chromosome met statisties betekenisvolle QTL is met aanvullende SSR merkers geteiken om die resolusie van kartering verder te verhoog. Die kwaliteit van fenotipiese data, soos in die proewe aangeteken, is bevestig deur korrelasies te bereken tussen lesings geneem deur onafhanklike plantpataloe (0.799 ± 0.023 vir reaksietipe en 0.942 ± 0.007 vir getransformeerde persentasie blaaroppervlakte besmet). Hoofeffek QTL vir die twee maatstawwe van weerstand is deur middel van die metodes van interval QTL kartering en gemodifiseerde interval QTL kartering konsekwent op chromosome 7D (25-48% van variasie verklaar) en 2B (21-46% van variasie verklaar) ge"identifiseer. In vorige studies is aangetoon dat beide chromosome 7D en 2B QTL vir volwasseplant streeproesweerstand dra. Die 7D QTL is waarskynlik die weerstandsgeen, Yr 18. QTL met klein effekte op weerstand is op chromosome lA en 4A ge"identifiseer. Die effek van laasgenoemde geen was meer prominent in die velddata in die vroee datum van weerstandsbeoordeling. Een QTL, afkomstig van 'Avocet S', is slegs onder groeikamertoestande identifiseerbaar. Dit dui op moontlike genotipe-omgewing wisselwerking en beklemtoon die noodsaaklikheid om aanpassings te maak in groeikamertoestande vir beter simulasie van veldproeftoestande. Die genetiese grondslag van volwasseplantweerstand teen streeproes in die kultivar 'Kariega' is deur QTL kartering bepaal. Die 'Kariega X Avocet S' koppelingskaart kan as 'n waardevolle basis dien vir toekomstige genetiese ontledings van ander polimorfiese kenmerke in die populasie.

La maladie de la rouille foliaire du peuplier, causée par le basidiomycète Melampsora larici-populina (Mlp) cause des dégâts importants dans les peupleraies européennes. Le séquençage du génome de la souche 98AG31 de Mlp a ouvert de nouvelles perspectives pour l'identification de déterminants géniques impliqués dans le processus infectieux du champignon et notamment ceux codant des effecteurs fongiques capables de manipuler la structure et le fonctionnement de la cellule hôte pour assurer le succès de l'infection. L'analyse du transcriptome du champignon au cours des différentes phases du processus infectieux, basée sur l'utilisation de puces à oligonucléotides NimbleGen ou le séquençage massifs d'ESTs, a permis d?identifier des gènes marqueurs de la germination, de la phase de croissance biotrophe et de la sporulation du champignon. Nous avons notamment pu montrer l'induction importante de nombreux gènes codant des petites protéines sécrétées (SSPs) au cours de la phase biotrophe à 96 hpi heures post-inoculation (hpi) ainsi qu'au sein du parenchyme lacuneux à 168 hpi par microdissection à capture laser. L?analyse fine du sécrétome de Mlp, basée sur l'annotation, l'évolution et l'expression des gènes codant des SSPs a permis de mettre à jour des effecteurs candidats. Certains, spécifiquement exprimés in planta ou présentant des homologies de séquence avec des effecteurs de rouilles ont été localisés au niveau de l'haustorium. De manière intéressante, d'autre gènes candidats appartenant à des familles multigéniques sous pression de sélection positive, sont riches en cystéines, spécifiquement exprimés in planta et possèdent un motif de translocation potentiellement impliqué dans l'export de l'effecteur dans la cellule hôte. Ce travail d'analyse fine des effecteurs potentiels d'un agent de rouille à l'échelle génomique va contribuer à l'amélioration des connaissances sur la biologie de ces champignons biotrophes et contribuera à faciliter la recherche de nouvelles méthodes de lutte contre la maladie / The leaf rust disease caused by Melampsora larici-populina (Mlp) is the main disease affecting poplar plantations in Europe with severe economic losses. The recent sequencing of the genome of Mlp (strain 98AG31) opens new perspectives to identify key genes involved in the fungal infection process and particularly those encoding fungal effectors that could manipulate host cell structure and function to facilitate host colonization. Analysis of the rust transcriptome during time course infection of poplar leaves, based on NimbleGen oligoarrays and massive EST sequencing led to the identification of genes related to fungal germination, biotrophy and sporulation. A consistant induction of genes encoding small-secreted proteins (SSPs) was observed during the biotrophic growth at 96 hours post-inoculation (hpi) but also at 168 hpi in the palisade mesophyll using laser capture microdissection. Mlp Secretome analysis, based on annotation, evolution and expression of genes encoding SSPs helped in identifying candidate poplar rust effectors. Some, specifically expressed in planta or showing homologies with known rust effectors were localized around the haustorium. Interestingly, other candidate genes, belonging to multigenic families under diversifying selection are cystein-rich, specifically expressed in planta and harbour a translocation signal potentially involved in effector export inside host cell. This genome-wide analysis of putative fungal effectors will contribute to the general knowledge of rust biology and will help to set new approaches to prevent and control the disease