No description available.

No description available.

Boreal forests are often strongly nitrogen (N) limited. However, human activities are leading to increased N inputs into these ecosystems, through atmospheric N deposition and forest fertilization. N input into boreal forests can promote net primary productivity, increase herbivore and pathogen damage, and shift plant species composition and community structure. Genetic diversity has been suggested as a key mechanism to promote a plant species’ stability within communities in response to environmental change. Within any plant population, specific traits (e.g. growth and defense traits) can vary substantially among individuals, and a greater variation in traits may increase chances for the persistence of at least some individuals of a population, when environmental conditions change. One aspect of plant chemistry that can greatly vary among different genotypes (GTs) are condensed tannin (CTs). These secondary metabolites have been suggested to affect plant performance in many ways, e.g. through influencing plant growth, the interactions of plants with herbivores and pathogens, and through affecting litter decomposition, and hence the return of nutrients to plants. To investigate how genotypic variation in foliar CT production may mediate the effects that anthropogenic N enrichment can have on plant performance and litter decomposition, I performed a series of experiments. For these experiments, aspen (Populus tremula) GTs with contrasting abilities to produce foliar CTs (i.e. low- vs. high-tannin producers) were grown under 3 N conditions, representing ambient N (+0 kg ha-1), upper level atmospheric N deposition (+15 kg ha-1), and forest fertilization rates (+150 kg ha-1). This general experimental set-up was once established in a field-like environment, from which natural enemies were excluded, and once in a field, in which enemies were present. In my first two studies, I investigated tissue chemistry and plant performance in both environments. I observed that foliar CT levels decreased in response to N in the enemy‑free environment (study I), but increased with added N when enemies were present (study II). These opposing responses to N may be explained by differences in soil N availability in the two environments, or by induction of CTs after enemy attack. Enemy damage generally increased in response to N, and was higher in low-tannin than in high-tannin plants across all N levels. Plant growth of high‑tannin plants was restricted under ambient and low N conditions, probably due to a trade-off between growth and defense. This growth constraint for high‑tannin plants was weakened, when high amounts of N were added (study I and II), and when enemy levels were sufficiently high, so that benefits gained through defense could outweigh the costs of defense production (study II). Despite those general responses of low- and high‑tannin producers to added N, I also observed a number of individual responses of GTs to N addition, which in some case were not connected to the intrinsic ability of the GTs to produce foliar CTs. In study III, gene expression levels in young leaves and phenolic pools of the plants that were grown in the enemy‑free environment were studied. This study revealed that gene control over the regulation of the phenylpropanoid pathway (PPP) was distributed across the entire pathway. Moreover, PPP gene expression was higher in high-tannin GTs than in low‑tannin GTs, particularly under ambient N. At the low N level, gene expressions declined for both low- and high-tannin producers, whereas at the high N level expression at the beginning and the end of the PPP was upregulated and difference between tannin groups disappeared. Furthermore, this study showed that phenolic pools were frequently uncorrelated, and that phenolic pools were only to some extent related to tannin production and gene expression. In study IV, I investigated the decomposability of litter from the field plants. I found that N enrichment generally decreased mass loss, but there was substantial genetic variation in decomposition rates, and GTs were differentially responsive to added N. Study IV further showed that CTs only had a weak effect on decomposition, and other traits, such as specific leaf area and the lignin:N ratio, could better explain genotypic difference in mass loss. Furthermore, N addition caused a shift in which traits most strongly influenced decomposition rates. Collectively, the result of these studies highlight the importance of genetic diversity to promote the stability of species in environments that experience anthropogenic change. / Boreala skogar är ofta mycket kväve (N) begränsade. Men mänskliga aktiviteter leder till ökad N tillförsel i dessa ekosystem, både genom depostition av N från atmosfären och skogsgödsling. N-tillförsel i boreala skogar kan främja netto primärproduktionen men även leda till ökade skador från naturliga fiender (herbivorer och patogener) samt skiftningar i växtartsammansättning. Genetisk mångfald har föreslagits som en viktig mekanism för att främja en växtarts stabilitet inom samhällen som upplever miljöförändringar. Inom varje växtpopulation kan specifika egenskaper (t.ex. tillväxt och försvar) varierar kraftigt mellan individer och en större variation i egenskaper kan öka chanserna för att åtminstone några individer från en population överlever ifall miljöförhållandena förändras. En aspekt av växtkemi som i hög grad kan variera mellan olika genotyper (GT) är bladens kondenserade tanniner (KT). Dessa sekundära metaboliter har föreslagits påverka växtens prestationsförmåga på många sätt, t.ex. genom att påverka tillväxt, interaktioner mellan växter och herbivorer eller patogener och genom att påverka förna nedbrytning, och följaktligen återbördandet av näringsämnen till kretsloppet. För att undersöka hur genotypiska variation i KT produktion kan påverka de effekter som antopogent N kan ha på växtens prestationsförmåga och förna nedbrytning, utförde jag en serie experiment. Jag studerade olika asp (Populus tremula) GT med olika förmåga att producera KT (låg- och hög-tannin producenter). Växterna odlades i tre olika N förhållanden, som representerade ambient N nivå (+0 kg ha-1), atmosfärisk N deposition = låg nivå (+15 kg ha-1), och skogsgödsling = hög nivå (150 kg ha‑1). Dessa GT etablerades i en fält-liknande miljö där naturliga fiender uteslutits och i ett fält där naturliga fiender var närvarande. I mina första två studierna undersökte jag vävnadskemi och växternas prestationsförmåga i de båda miljöerna. Jag observerade att KT nivåerna sjönk till följd av N‑tillsats i den fiende-fria miljön (studie I), men ökade med N-tillsats ifall fiender var närvarande (studie II). Dessa motsatta reaktioner på N-tillsats kan förklaras av skillnader i N-tillgång mellan de två odlingsplatserna eller genom ökad KT produktion som respons på angrepp. Skador orsakade av herbivorer och patogener ökade generellt till följd av N‑tillsats och var högre i låg-tannin än i hög‑tannin producerande GT oavsett N‑förhållande. Tillväxten hos växter från hög‑tannin GT begränsades i ambient- och låg N-tillsats förhållanden, troligen på grund av att avvägning mellan tillväxt och försvar förskjutits emot försvar. Den begränsade tillväxten i hög-tannin växter minskade om stora mängder N tillsattes (studie I och II) och om antalet fiender var tillräckligt högt så att nyttan av försvaret kunde uppväga kostnaderna för försvarsproduktionen (studie II). Trots dessa generella respons hos låg- och hög-tannin GT till följd av N‑tillsats observerade jag även ett antal individuella respons hos GT som i vissa fall var orelaterade till växters förmåga att producera KT. I studie III undersöktes genuttrycksnivåer och fenolinnehåll i blad från växter som odladats i en miljö där naturliga fiender exkluderats. Denna studie visade att fenylpropanoidsyntesvägen (FPV) regleras genom kontroll av många av de undersökta FPV-generna. Dessutom var FPV genuttryck högre i hög-tannin GT än i låg-tannin GT, särskilt vid ambient N. Vid låg N-tillsats minskade genuttrycket av FPV-gener i både låg- och hög-tannin producenter, medan hög N-tillgång ledde till att gener i början och slutet av FPV uppreglerades och till att skillnaderna mellan tannin grupperna försvann. Dessutom visade studien att de separata fenol-poolerna ofta var okorrelerade med varandra och att fenol-poolerna bara till viss del var korrelerade med KT produktion och FPV-genutryck. I studie IV undersökte jag nedbrytningshastigheten för förnan från fältodlade aspar. Jag upptäckte att N-tillsats generellt minskade viktförlusten men att det fanns en betydande genetisk variation mellan GT och att dessa även var olika mottagliga för tillsatt N. Studie IV visade vidare att KT endast hade en svag effekt på nedbrytning och att andra egenskaper såsom specifik bladyta och lignin:N ratio kunde bättre förklara den genotypiska skillnaden i viktförlust. Dessutom orsakade N‑tillsats en förskjutning av vilka egenskaper som mest påverkade förnans nedbrytningshastighet. Sammanfattningsvis visar mina studier på vikten av genetisk mångfald för att främja växtartens stabilitet i miljöer som upplever antropogena förändringar.

Le monoxyde d’azote (NO) régule un grand nombre de processus physiologiques tel quele développement ou les réponses aux modifications des conditions environnementales. Dans cetravail, la production de NO et ses effets ont été étudiés dans le contexte des interactions plante –pathogène. La production de NO générée chez Arabidopsis thaliana par les oligogalacturonides(OGs), eliciteur endogène des réactions de défense, a été mesurée par la sonde fluorescente 4, 5-diamino fluoresceine diacetate. L’utilisation d’approches pharmacologiques et génétiques ontpermis d’étudier les sources enzymatiques de la production de NO et son rôle dans l’interactionA. thaliana/Botrytis cinerea. Nous avons montré que le NO est produit par une voie dépendantede la L-arginine ainsi que d’une voie impliquant la Nitrate Réductase. La production de NOinduite par les OGs est dépendante du Ca2+ et modulée par les formes activées de l’oxygène(produites par AtRBOHD). La production de NO est également régulée par les CDPKs mais estindépendante des activités MAPKs. A l’aide d’une approche transcriptomique nous avons ensuitedémontré que le NO participe à la régulation de l’expression de gènes induits par les OGs tels quedes gènes codant pour des protéines PR ou des facteurs de transcription. La sur-représentation decertains éléments régulateurs (par exemple de type W-box) dans les régions promotrices desgènes cibles du NO suggère également l’implication de facteurs de transcription spécifiques dansla réponse au NO. Enfin, des plantes mutantes, affectées dans l’expression de gènes cibles de NO,ainsi que des plantes de type sauvage (Col-0) traitées par le piégeur de NO, cPTIO, sont plussensibles à B. cinerea. L’ensemble de ces résultats nous a permis de mieux comprendre lesmécanismes liant la production de NO, ses effets et la résistance d’A. thaliana à B. cinerea,confirmant que le NO est un élément-clé des réactions de défense des plantes / Nitric oxide (NO) regulates a wide range of plant processes from development toenvironmental adaptation. In this study, NO production and its effects were investigated in aplant-pathogen context. The production of NO following Arabidopsis treatment witholigogalacturonides (OGs), an endogenous elicitor of plant defense, was assessed using the NOsensitive probe 4, 5-diamino fluorescein diacetate. Pharmacological and genetic approaches wereused to analyze NO enzymatic sources and its role in the Arabidopsis thaliana /Botrytis cinereainteraction. We showed that NO production involves both a L-arginine- and a nitrate reductase(NR)-pathways. OGs-induced NO production was Ca2+-dependent and modulated RBOHDmediatedROS production. NO production was also regulated by CDPKs activities, but workedindependently of the MAPKs pathway. Using a transcriptomic approach, we further demonstratedthat NO participates to the regulation of genes induced by OGs such as genes encoding diseaserelatedproteins and transcription factors. The over-representation of certain regulatory elements(e.g. W-BOX) in promoter sequences of target genes also suggests the involvement of specifictranscription factors in the NO response. Mutant plants impaired in several selected NOresponsivegenes, as well as Col-0 plants treated with the NO scavenger cPTIO, were moresusceptible to B. cinerea. Taken together, our investigation deciphers part of the mechanismslinking NO production, NO-induced effects and basal resistance to Botrytis cinerea. Moregenerally, our data reinforce the concept that NO is a key mediator of plant defense responses

El foc bacterià és una malaltia que afecta a plantes de la família de la rosàcies, causada pel bacteri Erwinia amylovora. El seu rang d'hostes inclou arbres fruiters, com la perera, la pomera o el codonyer, i plantes ornamentals de gran interès comercial i econòmic. Actualment, la malaltia s'ha dispersat i es troba àmpliament distribuïda en totes les zones de clima temperat del món. A Espanya, on la malaltia no és endèmica, el foc bacterià es va detectar per primer cop al 1995 al nord del país (Euskadi) i posteriorment, han aparegut varis focus en altres localitzacions, que han estat convenientment eradicats. El control del foc bacterià, és molt poc efectiu en plantes afectades per la malaltia, de manera que es basa en mesures encaminades a evitar la dispersió del patogen, i la introducció de la malaltia en regions no endèmiques. En aquest treball, la termoteràpia ha estat avaluada com a mètode d'eradicació d'E. amylovora de material vegetal de propagació asimptomàtic. S'ha demostrat que la termoteràpia és un mètode viable d'eradicar E. amylovora de material de propagació. Gairebé totes les espècies i varietats de rosàcies mantingudes en condicions d'humitat sobrevivien 7 hores a 45 ºC i més de 3 hores a 50 ºC, mentre que més d'1 hora d'exposició a 50 ºC amb calor seca produïa danys en el material vegetal i reduïa la brotació. Tractaments de 60 min a 45 ºC o 30 min a 50 ºC van ser suficients per reduir la població epífita d'E. amylovora a nivells no detectables (5 x 102 ufc g-1 p.f.) en branques de perera. Els derivats dels fosfonats i el benzotiadiazol són efectius en el control del foc bacterià en perera i pomera, tant en condicions de laboratori, com d'hivernacle i camp. Els inductors de defensa de les plantes redueixen els nivells de malaltia fins al 40-60%. Els intervals de temps mínims per aconseguir el millor control de la malaltia van ser 5 dies pel fosetil-Al, i 7 dies per l'etefon i el benzotiadiazol, i les dosis òptimes pel fosetil-Al i el benzotiadiazol van ser 3.72 g HPO32- L-1 i 150 mg i.a. L-1, respectivament. Es millora l'eficàcia del fosetil-Al i del benzotiadiazol en el control del foc bacterià, quan es combinen amb els antibiòtics a la meitat de la dosi d'aquests últims. Tot i que l'estratègia de barrejar productes és més pràctica i fàcil de dur a terme a camp, que l'estratègia de combinar productes, el millor nivell de control de la malaltia s'aconsegueix amb l'estratègia de combinar productes. Es va analitzar a nivell histològic i ultrastructural l'efecte del benzotiadiazol i dels fosfonats en la interacció Erwinia amylovora-perera. Ni el benzotiadiazol, ni el fosetil-Al, ni l'etefon van induir canvis estructurals en els teixits de perera 7 dies després de la seva aplicació. No obstant, després de la inoculació d'E. amylovora es va observar en plantes tractades amb fosetil-Al i etefon una desorganització estructural cel·lular, mentre que en les plantes tractades amb benzotiadiazol aquestes alteracions tissulars van ser retardades. S'han avaluat dos models (Maryblyt, Cougarblight) en un camp a Espanya afectat per la malaltia, per determinar la precisió de les prediccions. Es van utilitzar dos models per elaborar el mapa de risc, el BRS-Powell combinat i el BIS95 modificat. Els resultats van mostrar dos zones amb elevat i baix risc de la malaltia. Maryblyt i Cougarblight són dos models de fàcil ús, tot i que la seva implementació en programes de maneig de la malaltia requereix que siguin avaluats i validats per un període de temps més llarg i en àrees on la malaltia hi estigui present. / Fire blight, caused by the bacterium Erwinia amylovora, is a serious disease of rosaceous plants that affects fruit trees such as pear, apple or quince, and ornamental plants with great commercial and economic interest. The disease is spread and well distributed in all temperate regions of the world. In Spain, where the disease is non endemic, fire blight was first detected in 1995 in the North of the country (Euskadi) and later, several new outbreaks have appeared in other locations that have been properly eradicated. Control of fire blight is very slightly effective in affected plants and is based on measures to avoid the spread of pathogen, and the introduction of disease in non-endemic regions. In this work, thermotherapy has been evaluated as a method for eradication of E. amylovora from symptomless propagating plant material. It has been demonstrated that heat is a viable method for eradicating E. amylovora from the propagation material of the pear. Almost all rosaceous species and cultivars maintained under moist conditions survived 7 hours at 45 ºC and up to 3 hours at 50 ºC, while more than 1 hour of exposure at 50 ºC under dry heat injured plants and reduced shooting. However, 60 min at 45 ºC or 30 min at 50 ºC were enough to reduce epiphytic E. amylovora population on pear budwoods to non-detectable level (5 x 102 cfu g-1 f.w.). Phosphonate derivatives and benzothiadiazole were effective in fire blight control in pear and apple, under laboratory, greenhouse and field conditions. Plant defense inducers reduced disease levels to 40-60%. The minimal time intervals to achieve the best control of disease were 5 days for fosetyl-Al, and 7 days for ethephon and benzothiadiazole, and the optimal doses of fosetyl-Al and benzothiadiazole were 3.72 g HPO32- L-1 and 150 mg a.i. L-1, respectively. The efficacy of fosetyl-Al and benzothiadiazole in fire blight control was improved when consecutively sprayed (combined strategy) with a half-reduced dose of antibiotics. Although the mixed strategy is more practical and easier to apply in the orchard than the combined one, the best level of fire blight control was achieved with the combined strategy. The effect of benzothiadiazole and phosphonates in Erwinia amylovora-pear interaction was analyzed at histological and ultrastructural level. Neither benzothiadiazole, nor fosetyl-Al, nor ethephon induced structural changes in pear leaf tissues 7 days after their application. However, after E. amylovora inoculation structural cell disorganization was observed in fosetyl-Al and ethephon-sprayed plants, while in benzothiadiazole-sprayed plants these tissue alterations were delayed. Two predictive models (Maryblyt and Cougarblight) were evaluated in an orchard naturally affected by fire blight in Spain, to determine the accuracy of the predictions. The combined BRS-Powell model and the modified BIS95 model were also evaluated. Results showed two clearly differentiated geographical areas with high and low fire blight risk. Maryblyt and Cougarblight are easy models to use, but their implementation in disease management programs must be evaluated and validated for more seasons and in areas where the disease is present.

Nitric oxide (NO) regulates a wide range of plant processes from development toenvironmental adaptation. In this study, NO production and its effects were investigated in aplant-pathogen context. The production of NO following Arabidopsis treatment witholigogalacturonides (OGs), an endogenous elicitor of plant defense, was assessed using the NOsensitive probe 4, 5-diamino fluorescein diacetate. Pharmacological and genetic approaches wereused to analyze NO enzymatic sources and its role in the Arabidopsis thaliana /Botrytis cinereainteraction. We showed that NO production involves both a L-arginine- and a nitrate reductase(NR)-pathways. OGs-induced NO production was Ca2+-dependent and modulated RBOHDmediatedROS production. NO production was also regulated by CDPKs activities, but workedindependently of the MAPKs pathway. Using a transcriptomic approach, we further demonstratedthat NO participates to the regulation of genes induced by OGs such as genes encoding diseaserelatedproteins and transcription factors. The over-representation of certain regulatory elements(e.g. W-BOX) in promoter sequences of target genes also suggests the involvement of specifictranscription factors in the NO response. Mutant plants impaired in several selected NOresponsivegenes, as well as Col-0 plants treated with the NO scavenger cPTIO, were moresusceptible to B. cinerea. Taken together, our investigation deciphers part of the mechanismslinking NO production, NO-induced effects and basal resistance to Botrytis cinerea. Moregenerally, our data reinforce the concept that NO is a key mediator of plant defense responses

Le lin, principale plante à fibres cultivée en France possède un intérêt industriel pour la qualité de ses fibres. Les cultures de lin sont régulièrement attaquées par un champignon tellurique, Fusarium oxysporum f. sp. lini (Fol), responsable des plus grandes pertes dans les cultures de lin. Les PGPR (Plant Growth Promoting Rhizobacteria) sont des bactéries réputées pour leurs capacités à améliorer la croissance et le développement des plantes, mais également pour leur pouvoir compétiteur au sein de la rhizosphère et leur aptitude à induire une réponse immunitaire chez les plantes. Parallèlement, l’utilisation de SDP (Stimulateur des Défenses des Plantes), molécules capables d’éliciter les mécanismes de défenses des plantes est une autre alternative pour limiter l’utilisation des pesticides. Dans le cadre de ce projet mené sur deux variétés de lin, Aramis et Mélina, il a pu être montré que Fol induisait un remodelage de la paroi au niveau des racines et des tiges, impliquant les hémicelluloses et les pectines, seulement deux jours après inoculation avec le champignon. L’utilisation de la souche ATCC 6633 de Bacillus subtilis comme agent de biocontrôle a permis de réduire de façon significative l’apparition des symptômes de la fusariose. Il a également été montré qu’en plus d’avoir un effet fongicide sur Fol, cette bactérie est capable d’induire l’expression de deux gènes de défense (Pathogenesis-Related) codant pour une β-(1,3)-glucanase (PR-2) et codant pour une chitinase-like (CTL-10), de gènes impliqués dans la voie des phénylpropanoïdes (PHENYLALANINE AMONIA LYASES, PAL-3 et PAL-4) et dans le remodelage pariétal (PECTIN METHYLESTERASE-3, PME-3) au niveau racinaire. Des analyses biochimiques ont également permis de montrer que B. subtilis provoque des modifications se traduisant par un renforcement pariétal au niveau des tiges chez les deux variétés. Enfin, l’association de la PGPR avec une molécule élicitrice (pregnénolone sulfate) a eu un effet synergique sur l’expression de gènes de défense. / In France, flax (Linum usitatissumum) is a principal fibers crop. Fusarium oxysporum f sp lini (Fol), a soil-borne fungus, is responsible for the major losses in crop yield. PGPR (Plant Growth Promoting Rhizobacteria) are known for their abilities to promote plant growth and health. These bacteria are also good competitors in the rhizosphere and can induce a plant defense response. The use of compounds able to elicit plant defense mechanisms is also an alternative to limit the use of pesticides. In this project, it has been shown that F. oxysporum f. sp. lini induces only two days after inoculation cell wall remodeling in the root and the stem involving hemicelluloses and pectins on two flax varieties, Aramis and Mélina, . The use of the Bacillus subtilis strain ATCC 6633 as biocontrol agent significantly reduced fusarium wilt appearance. In addition to its antifungal effect against Fol, this bacteria is able to induce the expression of two Pathogenesis-Related genes coding for a β-(1,3)-glucanase (PR-2) and a chitinase-like (CTL-10), genes involved in the phenylpropanoid pathway (PHENYLALANINE AMONIA LYASES, PAL-3 and PAL-4) and also in cell wall remodeling (PECTIN METHYLESTERASE-3, PME-3) in the root. Biochemical analyses show that B. subtilis causes modifications resulting in cell wall reinforcement in the stem in both varieties. Finally, the association of B. subtilis with an elicitor (pregnenolone sulfate) had a synergistic effect on the expression of defense-related genes.

No description available.

<p>  </p> <p>Environmental conditions, like light quality and herbivory, can induce changes in plant physiology. Light quality can be manipulated using LEDs (light emitting diodes) to improve crop quality and yield in horticultural production. The manipulation of light quality has also been utilized in the management of agricultural insect pests. Previous research has provided evidence that changes in light quality can have effects on the growth and chemistry of cannabis crops (<em>Cannabis spp.</em>). Varieties of cannabis are grown for the production of the valued cannabinoids CBD and THC. Pest of cannabis include herbivorous arthropods that reduce hemp yield and quality. Arthropod herbivory can induce chemical and physical changes in plants. This thesis further investigates the role of light quality on both cannabis biology and the crop-pest interaction between cannabis and the cannabis aphid (<em>Phorodon cannabis</em>). In the experiments described herein, the effects of light quality and <em>P. cannabis </em>herbivory on cannabis were assessed by measuring impact on biomass accumulation, yield, and the production of CBD and THC. The effects of light quality on the life history traits of <em>P. cannabis </em>were also measured. Cannabis grown under red-blue light quality saw a reduction in vegetative growth but no reduction in yield. Light treatments had no measured effect on the concentrations of CBD and THC in the cannabis buds. Aphid herbivory decreased bud yield but increased vegetative growth. Aphid herbivory reduced the concentration of both CBD and THC in cannabis bud tissue. Under blue-rich light quality, <em>P. cannabis </em>experienced higher reproductive rates when compared to red-blue and full-spectrum lighting. </p>