Plusieurs systématiques se côtoient aujourd'hui : la systématique typologique, d'inspiration linnéenne, qui repose sur l'examen morphologique de types porte-nom. Depuis plusieurs années, une systématique phylogénétique conduit également à la création de taxons nouveaux, de niveau spécifique, infra-spécifique et supra-spécifique. Dans ce travail, nous avons cherché une approche globale, qualifiée de taxonomie intégrative couplant les approches morphologiques traditionnelles, la systématique moléculaire et la geomorphométrie alaire, dans le but d'éclairer la notion d'espèce chez les Culicoides avec ses corollaires épidémiologiques, étant donnée l'importance de ces insectes dans des maladies majeures d'intérêt vétérinaire telles que la fièvre catarrhale ovine (FCO) et la maladie causée par le virus de Schmallenberg (SBV). Cette approche nous a permis de mettre en lumière la complexité systématique des espèces affines (C.clastrieri/C.festivipennis, les groupes Obsoletus, Pulicaris et Vexans). De plus, nous nous sommes intéressés aux préférences trophiques des Culicoides de la région Champagne-Ardenne. / Several systematic coexist today: typological systematic of Linnaean spirit, based on morphological examination of type specimens. For several years, a phylogenetic systematics also led to the creation of new taxa, at specific, sub-specific and supra-specific level.In this study, we have sought a comprehensive approach i.e. an integrative taxonomy that coupling traditional morphological approaches, molecular systematic and wing geometry morphometric in order to clarify the concept of species in the Culicoides with epidemiological corollaries, given the importance of these insects in major diseases of veterinary interest such as bluetongue (BT) and the disease caused by the Schmallenberg virus (SBV). This approach allowed us to highlight the systematic complexity of related species (C.clastrieri / C.festivipennis, the Obsoletus, Pulicaris and Vexans groups). In addition, we investigated the host preference of Culicoides of the Champagne-Ardenne region.

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter) is a widely distributed insect across the United States. Although, it feeds on several native wild hosts, its agricultural importance lies as an economic pest of cotton in several states in the southern United States. No studies have addressed intraspecific genetic and phenotypic variation of this insect pest at a large geographic scale. I examined genetic variation among cotton fleahopper populations associated with cotton in different geographic locations across the southern United States (Chapter II). Using dominant, neutral, nuclear molecular markers (AFLP, amplified fragment length polymorphism) and mitochondrial DNA sequences, I found that overall genetic differentiation among different geographic populations, collected from cotton in eleven cotton growing states, was low but significant. AFLP revealed the presence of three regional groups representing western (Arizona), central (Texas, Oklahoma, Arkansas, Louisiana, Mississippi and Alabama), and eastern (Florida, Georgia, South Carolina and North Carolina) populations. I examined if there were distinct lineages of cotton fleahoppers associated with three of its host plant species: cotton (Gossypium hirsutum), horsemint (Monarda punctata) and woolly croton (Croton capitatus) in five different locations of Texas by using AFLP markers (Chapter III). I found two distinct host-associated lineages at three locations and local panmixia in the other two locations. I tested if host preference of cotton fleahoppers were affected by geographic variation and prior experience. Conducting choice tests with a Y-tube olfactometer, I found that host preference in cotton fleahoppers for horsemint (one of its native host plants) is conserved and unaffected by individual?s prior experience with cotton (Chapter IV). Finally, I explored the role of host-plant species in morphological differentiation of the cotton fleahopper in two locations that differ in presence of distinct host-associated lineages. Using a geometric-morphometric approach, I detected significant effect of host plant and geography on body morphology and wing shape of cotton fleahopper populations (Chapter V). Length of antenna and rostrum were two important traits associated with morphological divergence of cotton and horsemint associated insect populations. Cotton associated individuals had relatively longer antenna and rostrum compared to individuals associated with horsemint.

<p>The mycorrhizal mutualism is one of the earliest and most influential of all terrestrial symbioses. As the primary method used by most plants to acquire nutrients from the soil, mycorrhizal fungi help to shape the structure and composition of many ecosystems. Ectomycorrhizal (EM) fungi play an especially significant role because most EM fungi prefer a limited number of host taxa, and EM plant species likewise associate with only a fraction of the available EM fungi. This host preference issue, combined with the high diversity of EM fungi in forest ecosystems, complicates interspecies competition both among fungi and among plants, because these plant and fungal communities interact.</p><p>Despite recent attempts at documenting mycorrhizal fungi in the context of ecological succession, many questions remain about the underlying causal relationships among EM fungi, soil conditions, and plant community assembly. The succession of mycorrhizal fungi often mirrors the succession of plants, and ectomycorrhizal (EM) community composition may affect the outcome of competition among trees during succession. In a pine-oak seral system, we tested the ability of <italic>Pinus taeda</italic> and <italic>Quercus alba</italic> seedlings to associate with EM fungi when planted under both conspecific and heterospecific adults. We found that EM communities under pine and oak canopy were distinct regardless of seedling identity, indicating that the fungal associations of adult trees determine which EM species are available in the soil. In addition, pine seedlings planted under oak canopy showed decreased mycorrhization and growth compared to those planted under pine canopy, while oak seedlings showed no negative effects of heterospecific planting. This impaired ability of pine seedlings to associate with the EM community established under oaks may deter pine recruitment and facilitate the late-seral replacement of pines with oaks.</p><p>While EM fungal communities correlate with the dominant species of host tree, soil properties do as well, making it difficult to establish causality among these three variables. Soil was collected from oak- and pine-dominated stands and dried to kill off mature mycelium, leaving only the spore bank as a source of inoculum for pine and oak seedlings. EM root tips were collected for molecular identification of fungal species based on ITS barcoding, and soil samples from field and laboratory conditions were analyzed for fungal diversity using 454 sequencing. We found a reduced influence of canopy type and a more pronounced influence of seedling identity when compared to the EM communities on seedlings planted in the field, suggesting that adult trees do alter the availability of fungi by directly promoting the growth of their preferred EM associates.</p><p>The availability of EM fungi can also affect seedlings at the interface between EM- an AM-dominated forest. We tested the hypothesis that seedlings of <italic>Dicymbe corymbosa</italic> which recruit outside of monodominant stands have limited access to EM symbionts compared with those which recruit inside <italic>D. corymbosa</italic> stands. EM root tips and rhizosphere soil were collected from seedlings along two transects inside monodominant stands and three transects in the transition zone into mixed forest dominated by AM associates. Seedlings inside monodominant stands yielded both a greater quantity of mycorrhized root tips and a higher diversity of EM species than transition zone seedlings. Of the fungal families commonly found on adult roots, the Boletaceae were notably underrepresented on all seedlings. In the transition zones, high-throughput sequencing of soil also detected a decrease in EM diversity with distance from the parent tree.</p><p>Seedlings of <italic>D. corymbosa</italic> may benefit from recruiting within monodominant stands by tapping into common mycorrhizal networks (CMNs) to acquire low-cost nitrogen and, potentially, photosynthates produced by conspecific adults. Leaves of stand adults, stand seedlings, and mixed-forest seedlings were collected for stable isotope analysis to track the transfer of nitrogen and carbon through CMNs. The &delta;<super>13</super>C and &delta;<super>15</super>N results contradicted each other, suggesting that more complicated interactions may be playing out among adults, seedlings, and fungi.</p> / Dissertation

Submitted by ONIEL JEREMIAS AGUIRRE GIL null (oaguirretm@outlook.com) on 2016-11-18T19:43:27Z No. of bitstreams: 1 Tese_Versão_definitiva_PDF.pdf: 2376464 bytes, checksum: 98c10cbf6c2dc00d45f713eb74c82f7f (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-11-24T15:13:11Z (GMT) No. of bitstreams: 1 gil_oj_dr_jabo.pdf: 2376464 bytes, checksum: 98c10cbf6c2dc00d45f713eb74c82f7f (MD5) / Made available in DSpace on 2016-11-24T15:13:11Z (GMT). No. of bitstreams: 1 gil_oj_dr_jabo.pdf: 2376464 bytes, checksum: 98c10cbf6c2dc00d45f713eb74c82f7f (MD5) Previous issue date: 2016-11-04 / Outra / Microcharops anticarsiae é um eficiente parasitoide da lagarta-dasoja Anticarsia gemmatalis que, também, parasita lagartas de outras espécies como Chrysodeixis includens e Spodoptera eridania. O objetivo do trabalho foi (1) determinar o ínstar larval de A. gemmatalis preferencialmente parasitado por M. anticarsiae a partir de lagartas coletadas em campo, (2) determinar o efeito de criações sucessivas de M. anticarsiae nos parâmetros biológicos do parasitoide e (3) determinar o efeito da soja transgênica sobre a longevidade de adultos do parasitoide. Os experimentos foram conduzidos nos anos agrícolas de 2014/15 e 2015/16 na FCAV/UNESP, Jaboticabal, SP, Brasil. Para a coleta das lagartas em campo, foram semeadas duas áreas de soja transgênica, uma tolerante ao herbicida glifosato e a outra resistente a insetos. Os resultados indicam que (1) M. anticarsiae preferiu parasitar lagartas de A. gemmatalis de primeiro e segundo ínstar em soja tolerante ao glifosato em campo, (2) não houve diferenças nos parâmetros biológicos de M. anticarsiae criado durante três gerações sucessivas em laboratório e (3) a longevidade total de M. anticarsiae e a longevidade de fêmeas foi mais longa em soja tolerante ao glifosato e a longevidade dos machos foi mais curta em ambas as sojas, tolerante ao glifosato e resistente a insetos. Finalmente, conclui-se que M. anticarsiae parasita lagartas de A. gemmatalis de primeiro e segundo ínstar em campo, que os parâmetros biológicos de M. anticarsiae não são afetados quando criados durante três gerações em laboratório e que a soja resistente a insetos afeta negativamente a longevidade dos machos de M. anticarsiae. / Microcharops anticarsiae is an efficient parasitoid of Anticarsiagemmatalis and also parasitizes larvae of other species such as Chrysodeixis includens and Spodoptera eridania. This work aimed to (1) determine the larval ínstar of A. gemmatalis preferentially parasitized by M. anticarsiae from larvae collected in the field, (2) determine the effect of successive laboratory rearings of M. anticarsiae in the biological parameters of the parasitoid, and (3) determine the effect of transgenic soybean in the longevity of adults of the parasitoid. the experiments were carried out in the seasons 2014/2015 and 2015/2016 in the FCAV/UNESP, Jaboticabal, SP, Brasil. Two areas were sown with transgenic soybean, the first one tolerant to glyphosate and the second one resistant to insects. The results indicate that (1) M. anticarsiae preferred to parasitize A. gemmatalis larvae on the first and second larval ínstar in soybean tolerant to glyphosate in the field, (2) there were not differences in the biological parameters of M. anticarsiae reared during three successive laboratory rearings, and (3) the longevity total of M. anticarsiae and longevity of females was longer in soybean tolerant to glyphosate and the longevity of males was shorter in soybean tolerant to glyphosate and resistant to insects. Finally, we conclude that M. anticarsiae parasitize first and second ínstar larvae of A. gemmatalis in the field, the biological parameters of M. anticarsiae are not affected when reared during three generations in the laboratory, and the soybean resistant to insects affects negatively the longevity of males M. anticarsiae.

Sacoglossan sea slugs are one of the best known examples of specialist herbivores in the marine environment and can be found strongly associated with their algal hosts and food sources. Perhaps the most intriguing characteristic of many sacoglossans is their ability to sequester functional chloroplasts from their algal food sources in a process called kleptoplasty. Despite this, there continues to be issues regarding taxonomic identification of species. In turn, the ecological characteristics of many of these slugs, such as algal host and food source preference, as well as their behavioral aspects, have received little attention. A prime example of these issues arises in one such kleptoplastic sacoglossan found at Sunset Beach, Tarpon Springs, USA. The slug had previously been identified as Elysia patina based on a recent description, but later evidence suggested this was incorrect. Furthermore, despite the evidence found for the slug’s photosynthetic capabilities, little was known of its ecological relationships and behavior. The purposes of this study were to: 1) correct the uncertain taxonomy of the Tarpon Springs slug previously identified as Elysia patina, and 2) explore the ecological and behavioral characteristics of the slug. First, a comparative study was performed between the Tarpon Springs slug and its original description, as well as descriptions for the superficially-similar congener slug, Elysia papillosa. The gross anatomy, dorsal surface vascular morphology, radular morphology, egg mass morphology, and developmental timeline of the Tarpon Springs slug were used as means of comparison with the previous descriptions. The results of the comparison show that the Tarpon Springs slug was in fact E. papillosa rather than E. patina, and that the most recent description used to identify the slug as E. patina was incorrect and should not be used. Second, a descriptive study of the ecological and behavioral aspects of E. papillosa at the Sunset Beach site were performed. From October 2014 to September 2015, bi-weekly algal collections were made to determine the seasonal abundance of the slug and a possible relationship between slug abundance and algal abundance. Next, a second collection study was performed bi-monthly from April to July 2016 to identify the preferred algal host of E. papillosa between the three most abundant rhizophytic algae at the site, Penicillus capitatus, Penicillus lamourouxii, and Halimeda incrassata, all of which have been previously reported as being hosts of E. papillosa. The results of these studies showed no relationship between slug abundance and algal abundance, however E. papillosa was found to have a seasonal population fluctuation, with the fewest slugs found in winter and summer months and the most slugs found in the spring and fall months, especially in April and May. Elysia papillosa was also found in significantly higher numbers on the alga P. capitatus compared to the other two algal species, although some slugs were found on P. lamourouxii. Only one slug was found on H. incrassata, indicating it is not being used as a host despite previous reports. Further exploration into the genetics of sequestered chloroplasts would provide critical details into E. papillosa’s feeding behavior in situ. Lastly, because of E. papillosa’s photosynthetic abilities, an experiment was performed to determine if E. papillosa exhibited phototactic behavior. Fully-fed slugs were found to have no preference for either light or dark conditions, indicating their behavior was not being influenced by their photosynthetic abilities. This information provides a means of comparison with future studies of the phototactic behavior of kleptoplastic slugs, and could provide insight into how the longevity of functional chloroplasts in each species of slug could influence their behavior.

Chez les insectes phytophages, la sélection de la plante-hôte qui constitue un site de ponte et d'alimentation est cruciale pour la survie et le bon développement de la descendance. Les sens chimiques – olfaction et gustation - sont déterminants pour un insecte lors du choix de sa plante hôte. Ainsi, une expérience olfacto-gustative des signaux chimiques d'une plante permet aux insectes d'optimiser la période de recherche et d'identification de celle-ci. Dans ce travail, nous avons testé l'effet d'une expérience pré-imaginale et imaginale pour un nouveau substrat de développement (enrichi en vanilline) sur l'induction de préférence olfactive et alimentaire à ce substrat chez trois espèces de lépidoptères foreurs de graminées ayant des spectres alimentaires différents, Sesamia nonagrioides (polyphage), Busseola fusca (oligophage) et Busseola nairobica (monophage). Il s'est avéré que la préférence olfactive des femelles pour les odeurs de ce substrat peut être induite par une expérience préalable pré-imaginale et imaginale pour ce nouveau substrat et que cette induction est transmise de façon transgénérationnelle. Elle n'est cependant pas liée à une augmentation de la sensitivité des antennes des femelles à la vanilline. De plus, elle dépend de l'espèce étudiée. Elle se manifeste plus rapidement chez l'espèce la plus polyphage (au bout de deux générations), plus tardivement chez l'espèce monophage (au bout de cinq générations) et est, par contre, absente chez l'espèce oligophage. Même si plusieurs mécanismes peuvent être impliqués dans cette induction, nos résultats valident à la fois la théorie d'Hopkins, le principe néo-Hopkins et l'héritage chimique chez les espèces qui ont présenté cette induction. Concernant les larves, nous avons pu montrer que celles-ci suivent, en général, la préférence olfactive des femelles pour les odeurs d'un nouveau substrat mais que cette préférence n'est pas corrélée avec leurs préférences alimentaires. / Among herbivorous insects, the selection of the host plant as an egg laying site and food is crucial for the survival and development of the offspring. The chemical senses - olfaction and gustation – of an insect are crucial in host plant selection. An olfactory-gustatory experience of plant chemical signals allows insects to optimize their search period and host identification. In this study, we tested the effect of pre-imaginal and imaginal experience for a new artificial diet (enriched in vanillin) on the induction of olfactory and food preference for this diet in three species of lepidopteran stem borers with different food spectra, namely Sesamia nonagrioides (polyphagous), Busseola fusca (oligophagous) and Busseola nairobica (monophagous). It was shown that the olfactory preference of females for the odor of the new diet could be induced by pre-imaginal and imaginal experience for this new diet and that this induction was transmitted transgenerationally. It was however not linked to an increase in the sensitivity of the female antennae to vanillin. In addition, it depended on the species studied. It occurred after two generations only in the polyphagous species, after five generations in the monophagous species, and it was absent in the oligophagous species. Although several mechanisms may be involved in this induction, our results validate both the theory of Hopkins, neo-Hopkins principle and the chemical legacy in the species in which the induction occurred. The larvae exhibited generally the same olfactory preference than the adult females for the odors of the new diet but this preference was not correlated with their food preferences, indicating in larvae a discrepancy between olfaction and gustation.

Phytoplasmas are bacteria with a persistent propagative transmission by insect vectors that generates direct and indirect interactions among them. In order to understand these interactions for maize bushy stunt phytoplasma (MBSP) and the leafhopper vector Dalbulus maidis (Hemiptera: Cicadellidae), two research lines were addressed. The first one aimed to determine the indirect effects of maize infection by MBSP on some biological and behavioral parameters of the vector, whereas a second line investigated direct interactions of the phytoplasma with D. maidis during its movement through the vector body following acquisition from plants, and associated microbiota. Indirect effects were investigated in choice experiments in which alighting and oviposition preferences by D. maidis were compared on healthy vs. MBSP-infected plants with variable incubation time (diseased plants with early and advanced symptoms, or still asymptomatic). Likewise, indirect effect of MBSP on the D. maidis biology was determined in two life table experiments in which the vector was reared on healthy vs. MBSP-infected plants expressing advanced disease symptoms or still asymptomatic. Choice experiments showed that alighting and oviposition preferences of D. maidis on MBSP-infected plants compared to healthy plants depend on the pathogen incubation period in the plant. The leafhopper preferred MBSP-infected plants over healthy ones during the asymptomatic phase of the disease, but rejected infected plants with advanced symptoms. The vector was able to acquire MBSP from asymptomatic infected plants shortly (3 days) after inoculation, but transmission efficiency increased when acquisition occurred at later stages of the pathogen incubation period (&ge;14 days) in the source plants and the test plants showed disease symptoms faster. These results suggest that MBSP modulates D. maidis preference for asymptomatic infected plants in the early stages of the crop, allowing rapid spread of this pathogen. Maize infection by the phytoplasma had a neutral effect on most life table parameters of D. maidis; a lower net reproductivity rate (Ro) was observed in the cohort reared on MBSP-infected plants with advanced symptoms, which was compensated to some extent by a higher sexual ratio. MBSP acquisition by all vector nymphal stadia was confirmed by PCR, and the pathogen as detected in both male and female reproductive organs. Concerning direct MBSP-vector interactions, transmission electron microscopy analyses showed phytoplasma-like cells in the midgut lumen, microvilli and epithelial cells, suggesting that MBSP enters the epithelium midgut through the microvilli wall. Within the epithelial cells, mitochondria and bacteria-like cells (possibly endosymbionts) were observed together with masses of phythoplasma-like cells. In the hemocoel, phytoplasma-like cells grouped into a matrix were also observed in association with bacteria-like cells similar to those observed in the midgut epithelium. Similar associations were found in the salivary gland. Interestingly, in-situ hybridization (FISH) technique revealed a variation in diversity and abundance of the microbiota in intestine and salivary glands of D. maidis adults over time after MBSP acquisition from plants. Sulcia sp., Cardinium sp. and eubacteria increased their abundance over time, whereas Rickettsia sp. decreased. The frequent association of the vector microbiota with the phytoplasma in some tissues of D. maidis suggests that endosymbiotic bacteria may play some role in MBSP-vector interactions. / Fitoplasmas são bactérias transmitidas de forma persistente propagativa por insetos vetores, havendo interações diretas e indiretas envolvendo tais organismos. Para entender algumas dessas interações no caso do enfezamento vermelho do milho, associado ao \'maize bushy stunt phytoplasma\' (MBPS) e à cigarrinha vetora Dalbulus maidis (Hemiptera: Cicadellidae), foram desenvolvidas duas linhas de trabalho. Na primeira determinou-se o efeito indireto de MBSP no comportamento e biologia do vetor, enquanto que na segunda estudaram-se as interações diretas do fitoplasma com o vetor durante sua movimentação através de órgãos internos e associação com a microbiota do inseto. O efeito indireto no comportamento foi demostrado em testes de escolha nos quais se variou o período de incubação de MBSP na planta (plantas com sintomas iniciais ou avançados da doença, e plantas infectadas assintomáticas) sobre a preferência para pouso e oviposição pelo vetor. O efeito indireto na biologia do D. maidis foi estabelecido em dois experimentos de tabela de vida, alimentando o inseto durante seu ciclo de vida em plantas de milho sadias ou plantas infectadas com o fitoplasma em dois tempos de incubação (plantas com sintomas avançados da doença e plantas infectadas assintomáticas). Os testes de escolha mostraram que a preferência de D. maidis para pouso e oviposição em plantas infectadas por MBSP em relação a plantas sadias depende do período de incubação do patógeno na planta. A cigarrinha preferiu plantas infectadas por MBSP na fase assintomática da doença, mas rejeitou plantas com sintomas avançados. Ocorreu aquisição do fitoplasma pelo vetor em plantas assintomáticas a partir de 3 dias após a inoculação, mas a eficiência de transmissão aumentou após 14 dias de incubação do patógeno na planta-fonte, e diminuiu o tempo para expressão de sintomas nas plantas-teste inoculadas. Os resultados sugerem que MBSP modula a preferência do vetor para plantas infectadas no estágio inicial da cultura de modo a permitir sua rápida disseminação. O efeito da infecção de plantas por MBSP na biologia de D. maidis mostrou ser neutro para a maioria dos parâmetros biológicos estimados; houve menor taxa líquida de reprodução (Ro), que foi compensada por maior razão sexual, para insetos criados em plantas com sintomas avançados. Verificou-se, por PCR, aquisição do fitoplasma por todos os estádios ninfais do vetor e sua presença em órgãos reprodutivos dos adultos. Por microscopia eletrônica de transmissão, observaram-se células do tipo fitoplasma no lúmen, microvilosidades e células epiteliais do mesêntero de D. maidis, sugerindo que o MBSP penetra no epitélio através das microvilosidades. No epitélio intestinal, foram observadas massas de células do tipo fitoplasma próximas a mitocôndrias e células bacterianas, possíveis endossimbiontes. Na hemocele, também foram observadas células do tipo fitoplasma agrupadas numa matriz, em associação com bactérias similares às observadas no intestino. Associações semelhantes foram observadas na glândula salivar. A técnica de FISH revelou uma variação na riqueza e abundância das espécies na da microbiota no mesêntero e glândula salivar de D. maidis em função do tempo após a aquisição de MBSP. A abundância de Sulcia sp., Cardinium sp. e eubacteria aumentou, enquanto que a de Rickettsia sp. decresceu. A associação frequente dessas bactérias com fitoplasma em alguns tecidos de D. maidis sugere que endossimbiontes possam ter um papel nas interações fitoplasma-vetor.

Phytoplasmas are bacteria with a persistent propagative transmission by insect vectors that generates direct and indirect interactions among them. In order to understand these interactions for maize bushy stunt phytoplasma (MBSP) and the leafhopper vector Dalbulus maidis (Hemiptera: Cicadellidae), two research lines were addressed. The first one aimed to determine the indirect effects of maize infection by MBSP on some biological and behavioral parameters of the vector, whereas a second line investigated direct interactions of the phytoplasma with D. maidis during its movement through the vector body following acquisition from plants, and associated microbiota. Indirect effects were investigated in choice experiments in which alighting and oviposition preferences by D. maidis were compared on healthy vs. MBSP-infected plants with variable incubation time (diseased plants with early and advanced symptoms, or still asymptomatic). Likewise, indirect effect of MBSP on the D. maidis biology was determined in two life table experiments in which the vector was reared on healthy vs. MBSP-infected plants expressing advanced disease symptoms or still asymptomatic. Choice experiments showed that alighting and oviposition preferences of D. maidis on MBSP-infected plants compared to healthy plants depend on the pathogen incubation period in the plant. The leafhopper preferred MBSP-infected plants over healthy ones during the asymptomatic phase of the disease, but rejected infected plants with advanced symptoms. The vector was able to acquire MBSP from asymptomatic infected plants shortly (3 days) after inoculation, but transmission efficiency increased when acquisition occurred at later stages of the pathogen incubation period (&ge;14 days) in the source plants and the test plants showed disease symptoms faster. These results suggest that MBSP modulates D. maidis preference for asymptomatic infected plants in the early stages of the crop, allowing rapid spread of this pathogen. Maize infection by the phytoplasma had a neutral effect on most life table parameters of D. maidis; a lower net reproductivity rate (Ro) was observed in the cohort reared on MBSP-infected plants with advanced symptoms, which was compensated to some extent by a higher sexual ratio. MBSP acquisition by all vector nymphal stadia was confirmed by PCR, and the pathogen as detected in both male and female reproductive organs. Concerning direct MBSP-vector interactions, transmission electron microscopy analyses showed phytoplasma-like cells in the midgut lumen, microvilli and epithelial cells, suggesting that MBSP enters the epithelium midgut through the microvilli wall. Within the epithelial cells, mitochondria and bacteria-like cells (possibly endosymbionts) were observed together with masses of phythoplasma-like cells. In the hemocoel, phytoplasma-like cells grouped into a matrix were also observed in association with bacteria-like cells similar to those observed in the midgut epithelium. Similar associations were found in the salivary gland. Interestingly, in-situ hybridization (FISH) technique revealed a variation in diversity and abundance of the microbiota in intestine and salivary glands of D. maidis adults over time after MBSP acquisition from plants. Sulcia sp., Cardinium sp. and eubacteria increased their abundance over time, whereas Rickettsia sp. decreased. The frequent association of the vector microbiota with the phytoplasma in some tissues of D. maidis suggests that endosymbiotic bacteria may play some role in MBSP-vector interactions. / Fitoplasmas são bactérias transmitidas de forma persistente propagativa por insetos vetores, havendo interações diretas e indiretas envolvendo tais organismos. Para entender algumas dessas interações no caso do enfezamento vermelho do milho, associado ao \'maize bushy stunt phytoplasma\' (MBPS) e à cigarrinha vetora Dalbulus maidis (Hemiptera: Cicadellidae), foram desenvolvidas duas linhas de trabalho. Na primeira determinou-se o efeito indireto de MBSP no comportamento e biologia do vetor, enquanto que na segunda estudaram-se as interações diretas do fitoplasma com o vetor durante sua movimentação através de órgãos internos e associação com a microbiota do inseto. O efeito indireto no comportamento foi demostrado em testes de escolha nos quais se variou o período de incubação de MBSP na planta (plantas com sintomas iniciais ou avançados da doença, e plantas infectadas assintomáticas) sobre a preferência para pouso e oviposição pelo vetor. O efeito indireto na biologia do D. maidis foi estabelecido em dois experimentos de tabela de vida, alimentando o inseto durante seu ciclo de vida em plantas de milho sadias ou plantas infectadas com o fitoplasma em dois tempos de incubação (plantas com sintomas avançados da doença e plantas infectadas assintomáticas). Os testes de escolha mostraram que a preferência de D. maidis para pouso e oviposição em plantas infectadas por MBSP em relação a plantas sadias depende do período de incubação do patógeno na planta. A cigarrinha preferiu plantas infectadas por MBSP na fase assintomática da doença, mas rejeitou plantas com sintomas avançados. Ocorreu aquisição do fitoplasma pelo vetor em plantas assintomáticas a partir de 3 dias após a inoculação, mas a eficiência de transmissão aumentou após 14 dias de incubação do patógeno na planta-fonte, e diminuiu o tempo para expressão de sintomas nas plantas-teste inoculadas. Os resultados sugerem que MBSP modula a preferência do vetor para plantas infectadas no estágio inicial da cultura de modo a permitir sua rápida disseminação. O efeito da infecção de plantas por MBSP na biologia de D. maidis mostrou ser neutro para a maioria dos parâmetros biológicos estimados; houve menor taxa líquida de reprodução (Ro), que foi compensada por maior razão sexual, para insetos criados em plantas com sintomas avançados. Verificou-se, por PCR, aquisição do fitoplasma por todos os estádios ninfais do vetor e sua presença em órgãos reprodutivos dos adultos. Por microscopia eletrônica de transmissão, observaram-se células do tipo fitoplasma no lúmen, microvilosidades e células epiteliais do mesêntero de D. maidis, sugerindo que o MBSP penetra no epitélio através das microvilosidades. No epitélio intestinal, foram observadas massas de células do tipo fitoplasma próximas a mitocôndrias e células bacterianas, possíveis endossimbiontes. Na hemocele, também foram observadas células do tipo fitoplasma agrupadas numa matriz, em associação com bactérias similares às observadas no intestino. Associações semelhantes foram observadas na glândula salivar. A técnica de FISH revelou uma variação na riqueza e abundância das espécies na da microbiota no mesêntero e glândula salivar de D. maidis em função do tempo após a aquisição de MBSP. A abundância de Sulcia sp., Cardinium sp. e eubacteria aumentou, enquanto que a de Rickettsia sp. decresceu. A associação frequente dessas bactérias com fitoplasma em alguns tecidos de D. maidis sugere que endossimbiontes possam ter um papel nas interações fitoplasma-vetor.

La découverte du rôle des insectes en tant que vecteurs de pathogènes, établi depuis plus d'un siècle, a été l'élément moteur de la discipline « entomologie médicale et vétérinaire ». Malgré le succès de nombreuses campagnes de prévention et de programmes de lutte, nous assistons depuis une trentaine d'années à l'émergence et à la recrudescence de maladies à transmission vectorielle. Le virus de la fièvre catarrhale ovine (FCO) (Reoviridae : Orbivirus) est un très bon exemple de virus émergent en Europe dont les mécanismes de transmission sont encore peu connus dans cette région. Ce virus est transmis par des moucherons hématophages du genre Culicoides (Diptera : Ceratopogonidae) aux ruminants sauvages et domestiques. En Europe, la FCO a été pendant longtemps considérée comme une maladie exotique. À partir de 1998, plusieurs incursions apparaissent dans l'ouest du bassin méditerranéen en lien avec la remontée vers le nord de populations de Culicoides imicola, le principal vecteur afrotropical. À partir d'août 2006, l'apparition et la transmission du sérotype 8 dans le nord de l'Europe, dans des zones où C. imicola est absent, révèle l'importance des espèces autochtones et la nécessité de comprendre leur rôle vecteur. Ce travail s'intéresse aux mécanismes de transmission du virus de la FCO en Europe non méditerranéenne, en i) présentant un état de l'art de la biologie et l'écologie des Culicoides adultes, ii) en évaluant les conditions possibles d'utilisation de pièges pour estimer le taux de piqûre et iii) en décrivant les comportements trophiques pour les espèces d'intérêt vétérinaire. / The discovery of insects as pathogens vectors was established for over a century and was the driving force behind the discipline “medical and veterinary entomology”. Despite the success of some prevention and control program campaigns, the emergence and spread of vector-borne diseases occurred dramatically during this last thirty years. Bluetongue virus (BTV) (Reoviridae: Orbivirus) is a good example of emerging virus in Europe, with a little understanding of the epidemiology of this disease. This virus is transmitted by blood-sucking midges of the genus Culicoides (Diptera: Ceratopogonidae) to wild and domestic ruminants. In Europe, BT was considered an exotic disease. In 1998, several incursions appeared in the western Mediterranean Basin in line with the northward progression of C. imicola populations, the main afrotropical vector. From August 2006, the emergence and transmission of serotype 8 in northern Europe, in areas where C. imicola is absent, revealed the importance of autochthonous species and the urgent need to understand their role as vector. This work gives new insights into the understanding of BTV transmission in northern Europe: i) presenting a state of the art review of the biology and ecology of Culicoides adults, ii) assessing different methods to study the biting rate and iii) highlighting trends in host-seeking behavior.

Certain crop plants are susceptible to pathogens or unable to develop efficient microbial symbioses. These crops adversely impact soil biological quality with consequences on plant health and productivity of cropping systems. Chickpea is a rotational pulse crop with two types: kabuli and desi, and several cultivars. Cultivation of chickpea has inconsistent effects on soil microbial communities and subsequent wheat crops. I conducted field studies and used high throughput molecular analyses to explore the variations among chickpeas to identify cultivars developing fungal communities that are conducive to plant health and productivity. I also carried out greenhouse studies and used biochemical analyses to investigate the response of chickpea cultivars to arbuscular mycorrhizal (AM) fungi and non-AM fungal endophytes and identify the influence of root and root metabolites on the endophytic and pathogenic fungi. Cultivars and types of chickpeas and environmental conditions promoted different fungal communities in the root endosphere. Funneliformis and Claroideoglomus were the dominant AM fungal genera and Fusarium and Alternaria were the dominant non-AM fungal genera in the roots of chickpea. The roots of cultivars CDC Corrine, CDC Cory and CDC Anna hosted the most diverse fungal communities in contrast to CDC Alma and CDC Xena roots which hosted the least diverse communities. Plant response to AM and non-AM fungal endophytes varied with genotype and type of chickpea. The root symbiosis effectively promoted plant growth in CDC Cory, CDC Anna and CDC Frontier and stimulated nitrogen fixation in CDC Corrine. Cultivars of chickpea responded differently to dual inoculation of the AM and non-AM fungal endophytes. Co-inoculation with AM and non-AM fungal endophytes had additive effects on CDC Corrine, CDC Anna and CDC Cory but non-AM fungal endophytes reduced the positive effect of AM fungi in Amit and CDC Vanguard. Desi chickpea appeared to form more efficient symbioses with soil fungal resources than kabuli chickpea. Protein(s) up-regulated in the mycorrhizal roots of the desi chickpea CDC Anna suppressed the growth of the fungal endophytes Trichoderma harzianum and Geomyces vinaceus and of the pathogens Fusarium oxysporum and Rhizoctonia sp. The formation of AM symbiosis decreased the production of root bioactive metabolites soluble in 25% methanol. Some of the root metabolites stimulated the growth of Trichoderma harzianum and Geomyces vinaceus, and a few inhibited Rhizoctonia sp. and Fusarium oxysporum. A few metabolites with contrasting effects on the different fungal species were detected. The non-protein phytochemicals had selective effects on the endophytes and pathogens whereas the antifungal proteins of mycorrhizal roots were non-selective. Overall the study reveals a "genotype effect" of chickpea on the soil microbiota suggesting the possibility to improve the performance of this crop through the selection of genotypes improving the communities of root associated fungi, by associating and responding to beneficial fungi and repressing the pathogens.