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In Integrated Pest Management programs, insecticides are applied to agricultural crops when pest densities exceed a predetermined economic threshold. Under conditions of high natural enemy density, however, the economic threshold can be increased, allowing for fewer insecticide applications. These adjustments, called ‘dynamic thresholds’, allow farmers to exploit existing biological control interactions without economic loss. Further, the ability of natural enemies to disperse from, and subsequently immigrate into, insecticide-sprayed areas can affect their biological control potential. We develop a theoretical approach to incorporate both pest and natural enemy movement across field borders into dynamic thresholds and explore how these affect insecticide applications and farmer incomes. Our model follows a pest and its specialist natural enemy over one growing season. An insecticide that targets the pest also induces mortality of the natural enemy, both via direct toxicity and reduced resource pest densities. Pest and natural enemy populations recover after spraying through within-field reproduction and by immigration from neighboring unsprayed areas. The number of insecticide applications and per-season farmer revenues are calculated for economic thresholds that are either fixed (ignoring natural enemy densities) or dynamic (incorporating them). The model predicts that using dynamic thresholds always leads to reduced insecticide application. The benefit of dynamic thresholds in reducing insecticide use is highest when natural enemies rapidly recolonize sprayed areas, and when insecticide efficacy is low. We discuss real-life situations in which monitoring of natural enemies would substantially reduce insecticide use and other scenarios where the presence of beneficial organisms may lead to threshold modifications.

The knowledge on symbiotic microorganisms of insects has increased in recent years, yet relatively little data is available on non-pathogenic viruses. Here we studied the virome of the parasitoid wasp Anagyrus vladimiri (Hymenoptera: Encyrtidae), a biocontrol agent of mealybugs. By high-throughput sequencing of viral nucleic acids, we revealed three novel viruses, belonging to the families Reoviridae (provisionally termed AnvRV [Anagyrus vladimiri reovirus]), Iflaviridae (AnvIFV) and Dicistroviridae (AnvDV). Phylogenetic analysis further classified the AnvRV in the genus Idnoreovirus, and the AnvDV in the genus Triatovirus. The genome of AnvRV is comprised of 10 distinct genomic segments ranging in length from 1.5 to 4.2 Kbp, but only two out of the 10 open reading frames (ORFs) have a known function. AnvIFV and AnvDV each have one polypeptide ORF, which is typical to iflaviruses but very un-common among dicistroviruses. AnvRV was found to be fixed in a mass-reared population of A. vladimiri, whereas it’s prevalence in field-collected wasps was ~15%. Similarly, the prevalence of AnvIFV and AnvDV were much higher in the mass rearing population than in the field population. Transmission electron micrographs of females’ ovaries revealed clusters and viroplasms of Reovirus-like particles in follicle cells. AnvRV was not detected in the mealybugs, suggesting that this virus is truly associated with the wasps. The possible effects of these viruses on A. vladimiri’s biology, and on biocontrol agents in general are discussed. Our findings identify RNA viruses as potential players involved in the multitrophic system of mealybugs, their parasitoids and other members of the holobiont.ImportanceDifferent biological control approaches use industrially mass-reared natural enemy insects to reduce damage of arthropod pests. Such mass-reared cultures may be positively and/or negatively affected by various microorganisms, including viruses. Yet, current knowledge on virus diversity, especially in arthropods, is limited. Here, we provide the first virome characterization of a member of the wasps family Encyrtidae - the member being the parasitoid Anagyrus vladimiri - a commercially important natural enemy of mealybug pests. We describe the genome of three previously unknown RNA viruses, co-inhabiting this parasitoid, and elaborate on the prevalence of those viruses in individual wasps of both mass-reared and environmental origins. Microscopy images suggest that at least one of the viruses is transmitted maternally via the ovaries. We discuss the genomic structure of the viruses and the possible relationship between those viruses and the A. vladimiri host, with implications on improvement of biocontrol of mealybug pests.

International audience; Pectobacterium brasiliense (Pbr) infects a wide range of crops worldwide, causing potato blackleg and soft rot and vegetable soft rots. This study aimed to characterize the genetic diversity and virulence variability among 68 Pbr strains isolated from either symptomless potato progeny tubers, diseased potato plants, ware potatoes wash water, or vegetables grown in Israel, as well as strains isolated from symptomless seed tubers grown in Europe, or diseased potato plants grown in France. The collection was typed using PCR and TaqMan real-time PCR analyses, dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), and pectolytic activity. dnaX phylogeny grouped almost all strains in a common genetic clade related to Pbr, which was distinct from the other Pectobacterium species. PFGE analysis identified two main clusters, including one major group of 47 strains with 95%-100% similarity. Maceration assays on two potato cultivars showed significant differences between strains but with no correlations with the source of the strains nor the status of the host (with/without symptoms). Molecular (dnaX sequences and PFGE profiles) and phenotypic analyses (tuber maceration tests) showed that the tested Pbr strains are not a homogeneous group. Analysis of the tested Pbr strains isolated from potato and vegetables grown in fields with a history of potato cultivation suggests that seed tubers imported from Europe may be the main source for Pbr in Israel. To the best of our knowledge, this is the first study that describes biodiversity and population structure of P. brasiliense isolated from potato and vegetables under hot climate conditions

International audience; The small ruminant (SR) value chain in Europe is a complex matrix of stakeholders with very different interests and profiles where it is not possible to establish one-size-fits-all solutions. The aim of this paper is to present the TechCarestrategies to manage animal welfare using innovative technologies, that are investigated through a multi-actor approach which takes into account the local SR production systems and involves all relevant stakeholders, from farmers totransporters, slaughterhouse, consumers and regulators. This co-design approach aims to: (1) Identify all relevant actors in SR value chain and train facilitators to engage stakeholders in continuous interaction and feedback to the rest of the project activities; (2) explore attitudes, behavioural dynamics and perceptions of stakeholders and their implications for prioritizing welfare issues and using innovative technologies to manage animal welfare at different production stages, and analyse the sustainability of the identified technologies by exploring their environmental, social, economic and cultural impacts. A series of engagements (i.e. one-on-one interviews, focus groups, questionnaires, nominal grouptechniques, concept mapping, etc.) will be set at regular stages in the project, for consultation and exchange of ideas and thus allowing co-design and co-innovation in a multi-actor approach. Among those, two national workshops peryear are planned in each of the nine partner countries to allow feedback and to effectively design business models and develop training and dissemination activities.

International audience; Knowledge on the use of PLF technologies (Tech) at different levels of the value chain for small ruminants (SR) was updated. Their uses for addressing animal welfare (Care) were analysed with a scientific literature review (SciRev).Keywords (n=67) were identified and SciRev was launched by TechCare partners, using several engines. A total of 991 abstracts were identified. Records entailing both Tech and Care (TC papers) were retained and classifiedaccording to the Tech and targeted Care indicators, animal species, production type and farming system. The outcome was a shared database compiling details of 368 TC for which a corresponding Mendeley PDF database was builtand made available online. Preliminary analyses shows that most frequent Care issues are related to malnutrition (monitored by behavioural sensors), general or chronic fear, transport and heat stress. Image analysis (video camera)is the most quoted Tech, followed by GPS (mainly for animal geo-referencing), accelerometry, heart rate measures and ultrasonography. Many technologies are used to monitor the same Care issue. The range of Tech is narrower foradequate housing, where environmental sensors are often coupled with body thermal condition/emission. There are few Tech for detecting mastitis, lameness and endoparasites. Preliminary results suggest that early warning systemsbased on different interoperating sensors are needed to effectively monitor welfare issues such as malnutrition. Further research is required to match effectively Tech and prioritised Care issues in the context of TechCare project.

International audience; Rural economies across Europe, and associated countries, heavily rely on small ruminant (SR) systems, particularly in areas unsuitable for other agriculture livestock production systems. Despite recent advances in precision livestock farming (PLF) and digital technologies (DT) to facilitate farm management, there is a slow rate of uptake by SR producers. This paper presents the project Sm@RT, which aims to improve the understanding, awareness and uptake of different technologies currently available to the SR sector, and further to facilitate ‘solutions to needs’ and identification of technology gaps. Sm@RT focus is on the use of PLF and DT across all types of sheep and goat management systems and environments, to develop a long-term, self-sustainable European/International network to encouragethe use of PLF and DT across the sectors. Eight countries (UK, Ireland, Norway, Estonia, France, Italy, Hungary, Israel) are involved in Sm@rt. The paper presents the original project’s approach: an interactive transdisciplinary and multi-actor approach relying on well-equipped demonstration farms (‘digifarms’) and innovative commercial farms to foster exchanges within the SR industry. It is an iterative step-by-step approach to engage relevant actors from all stakeholder groups at the appropriate level in the knowledge exchange process, crucial to boost dissemination in a trusting environment. Sm@RT will create opportunities to collect and exchange technical and practical knowledge, with information and guidelines on how to use PLF and DT to gain the best benefits for SR systems of production. This will increase efficiency and sustainability of SR farming systems in Europe and beyond.

The World Health Organization Global Action Plan recommends integrated surveillance programs as crucial strategies for monitoring antibiotic resistance. Although several national surveillance programs are in place for clinical and veterinary settings, no such schemes exist for monitoring antibiotic-resistant bacteria in the environment. In this transnational study, we developed, validated, and tested a low-cost surveillance and easy to implement approach to evaluate antibiotic resistance in wastewater treatment plants (WWTPs) by targeting cefotaxime-resistant (CTX-R) coliforms as indicators. The rationale for this approach was: i) coliform quantification methods are internationally accepted as indicators of fecal contamination in recreational waters and are therefore routinely applied in analytical labs; ii) CTX-R coliforms are clinically relevant, associated with extended-spectrum β-lactamases (ESBLs), and are rare in pristine environments. We analyzed 57 WWTPs in 22 countries across Europe, Asia, Africa, Australia, and North America. CTX-R coliforms were ubiquitous in raw sewage and their relative abundance varied significantly (

The broad variability of Cucumis melo (melon, Cucurbitaceae) presents a challenge to conventional classification and organization within the species. To shed further light on the infraspecific relationships within C. melo, we compared genotypic and metabolomic similarities among 44 accessions representative of most of the cultivar-groups. Genotyping-by-sequencing (GBS) provided over 20,000 single-nucleotide polymorphisms (SNPs). Metabolomics data of the mature fruit flesh and rind provided over 80,000 metabolomic and elemental features via an orchestra of six complementary metabolomic platforms. These technologies probed polar, semi-polar, and non-polar metabolite fractions as well as a set of mineral elements and included both flavor-and taste-relevant volatile and non-volatile metabolites. Together these results enabled an estimate of “metabolomic/elemental distance” and its correlation with the genetic GBS distance of melon accessions. This study indicates that extensive and non-targeted metabolomics/elemental characterization produced classifications that strongly, but not completely, reflect the current and extensive genetic classification. Certain melon Groups, such as Inodorous, clustered in parallel with the genetic classifications while other genome to metabolome/element associations proved less clear. We suggest that the combined genomic, metabolic, and element data reflect the extensive sexual compatibility among melon accessions and the breeding history that has, for example, targeted metabolic quality traits, such as taste and flavor. Fil: Moing, Annick. Universite de Bordeaux; Francia Fil: William Allwood, J.. The James Hutton Institute; Reino Unido Fil: Aharoni, Asaph. Weizmann Institute Of Science Israel; Israel Fil: Baker, John. Rothamsted Research; Reino Unido Fil: Beale, Michael H.. Rothamsted Research; Reino Unido Fil: Ben-Dor, Shifra. Weizmann Institute Of Science Israel; Israel Fil: Biais, Benoît. Universite de Bordeaux; Francia Fil: Brigante, Federico Iván. Max Planck Institute Of Molecular Plant Physiology; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencia y Tecnología de Alimentos Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Ciencia y Tecnología de Alimentos Córdoba; Argentina Fil: Burger, Yosef. Agricultural Research Organization Of Israel; Israel Fil: Deborde, Catherine. Universite de Bordeaux; Francia Fil: Erban, Alexander. Max Planck Institute Of Molecular Plant Physiology; Alemania Fil: Faigenboim, Adi. Agricultural Research Organization Of Israel; Israel Fil: Gur, Amit. Agricultural Research Organization Of Israel; Israel Fil: Goodacre, Royston. University of Liverpool; Reino Unido Fil: Hansen, Thomas H.. Universidad de Copenhagen; Dinamarca Fil: Jacob, Daniel. Universite de Bordeaux; Francia Fil: Katzir, Nurit. Agricultural Research Organization Of Israel; Israel Fil: Kopka, Joachim. Max Planck Institute Of Molecular Plant Physiology; Alemania Fil: Lewinsohn, Efraim. Agricultural Research Organization Of Israel; Israel Fil: Maucourt, Mickael. Universite de Bordeaux; Francia Fil: Meir, Sagit. Weizmann Institute Of Science Israel; Israel Fil: Miller, Sonia. Rothamsted Research; Reino Unido Fil: Mumm, Roland. Wageningen University & Países Bajos Fil: Oren, Elad. Agricultural Research Organization Of Israel; Israel Fil: Paris, Harry S.. Agricultural Research Organization Of Israel; Israel Fil: Rogachev, Ilana. Weizmann Institute Of Science Israel; Israel Fil: Rolin, Dominique. Universite de Bordeaux; Francia Fil: Saar, Uzi. Agricultural Research Organization Of Israel; Israel Fil: Schjoerring, Jan K.. Universidad de Copenhagen; Dinamarca Fil: Tadmor, Yaakov. Agricultural Research Organization Of Israel; Israel Fil: Tzuri, Galil. Agricultural Research Organization Of Israel; Israel Fil: de Vos, Ric C. H.. Wageningen University & Países Bajos Fil: Ward, Jane L.. Rothamsted Research; Reino Unido Fil: Yeselson, Elena. Agricultural Research Organization Of Israel; Israel Fil: Hall, Robert D.. Wageningen University & Países Bajos Fil: Schaffer, Arthur A.. Agricultural Research Organization Of Israel; Israel

Zucchini yellow mosaic virus (ZYMV; potyviridae) represents a major pathogen of Cucurbitaceae crops. ZYMV resistance in melon PI 414723 is conditioned by a dominant allele at the Zym locus. This resistant accession restricts viral spread and does not develop mosaic symptoms, but necrosis sometimes develops in response to inoculation. In previous studies, Zym has been mapped to linkage group II of the melon genetic map. In the present study, positional cloning of the locus was undertaken, starting from the CM-AG36 SSR marker at approximately 2 cm distance. We utilized five mapping populations that share the same resistant parent, PI 414723, and analyzed a total of 1630 offspring, to construct a high-resolution genetic map of the Zym locus. Two melon BAC libraries were used for chromosome walking and for developing new markers closer to the resistance gene by BAC-end sequencing. A BAC contig was constructed, and we identified a single BAC clone, from the ZYMV susceptible genotype MR-1, that physically encompasses the resistance gene. A second clone was isolated from another susceptible genotype, WMR 29, and the two clones were fully sequenced and annotated. Additional markers derived from the sequenced region delimited the region to 17.6 kb of a sequence that harbors a NAC-like transcription factor and, depending on the genotype, either two or three R-gene homologs with a CC-NBS-LRR structure. Mapping was confirmed by saturating the map with SNP markers using a single mapping population. The same region was amplified and sequenced also in the ZYMV resistant genotype PI 414723. Because numerous polymorphic sites were noted between genotypes, we could not associate resistance with a specific DNA polymorphism; however, this study enables molecular identification of Zym and paves the way to functional studies of this important locus.

International audience; Sugar from nectar or from honeydew can prolong parasitoids’ lifespan, enhance their fecundity and foraging ability, and thereby increase their pest suppression efficiency. Sugar sources within crop monocultures are considered to be limiting for parasitoids. Nevertheless, only few studies have measured the sugar feeding of parasitoid assemblages in agricultural areas or in surrounding non-crop habitats. We used cold anthrone tests to compare the frequency of sugar feeding in parasitoid communities, inside pomegranate orchards and in adjacent natural areas, over two consecutive years. Overall, 40% of the 1610 sampled individuals belonging to 135 species scored positive for sugar. Sugar-feeding frequency was lower within the orchards than in the neighbouring natural areas. The proportion of sugar-fed wasps increased with herbaceous vegetation cover, both within and outside the orchards, suggesting that herbs are a sugar-rich habitat. Parasitoids sampled from trees and from herbs within the orchards had similar frequencies of sugar feeding, despite differences in wasp species composition. Our results probably overestimate sugar-feeding frequencies in the field because sugar-fed individuals have higher longevity and hence are more likely to be sampled. We propose a simple model to approximate this over-sampling bias and apply it to Encarsia inaron (Aphelinidae), one of the most abundant parasitoids in the samples. We conclude that sugar availability potentially limits parasitoid fitness in this agro-ecosystem. This may be due to the low density of plants in natural areas during the Mediterranean summer, and to herbicide applications within the orchards that further suppress non-crop herbs.

International audience

Melon is an economically important fruit crop that has been cultivated for thousands of years; however, the genetic basis and history of its domestication still remain largely unknown. Here we report a comprehensive map of the genomic variation in melon derived from the resequencing of 1,175 accessions, which represent the global diversity of the species. Our results suggest that three independent domestication events occurred in melon, two in India and one in Africa. We detected two independent sets of domestication sweeps, resulting in diverse characteristics of the two subspecies melo and agrestis during melon breeding. Genome-wide association studies for 16 agronomic traits identified 208 loci significantly associated with fruit mass, quality and morphological characters. This study sheds light on the domestication history of melon and provides a valuable resource for genomics-assisted breeding of this important crop., This work was supported by funding from the Agricultural Science and Technology Innovation Program (to Yongyang Xu, S.H., Z.Z. and H.W.), the China Agriculture Research System (CARS-25 to Yongyang Xu and H.W.), the Leading Talents of Guangdong Province Program (00201515 to S.H.), the Shenzhen Municipal (The Peacock Plan KQTD2016113010482651 to S.H.), the Dapeng district government, National Natural Science Foundation of China (31772304 to Z.Z.), the Science and Technology Program of Guangdong (2018B020202007 to S.H.), the National Natural Science Foundation of China (31530066 to S.H.), the National Key R&D Program of China (2016YFD0101007 to S.H.), USDA National Institute of Food and Agriculture Specialty Crop Research Initiative (2015-51181-24285 to Z.F.), the European Research Council (ERC-SEXYPARTH to A.B.), the Spanish Ministry of Economy and Competitiveness (AGL2015–64625-C2-1-R to J.G.-M.), Severo Ochoa Programme for Centres of Excellence in R&D 2016–2010 (SEV-2015–0533 to J.G.-M.), the CERCA Programme/Generalitat de Catalunya to J.G.-M. and the German Science Foundation (SPP1991 Taxon-OMICS to H.S.).

International audience; Bacterial endosymbiosis is an important evolutionary process in insects, which can harbor both obligate and facultative symbionts. The evolution of these symbionts is driven by evolutionary convergence, and they exhibit among the tiniest genomes in prokaryotes. The large host spectrum of facultative symbionts and the high diversity of strategies they use to infect new hosts probably impact the evolution of their genome and explain why they undergo less severe genomic erosion than obligate symbionts. Candidatus Hamiltonella defensa is suitable for the investigation of the genomic evolution of facultative symbionts because the bacteria are engaged in specific relationships in two clades of insects. In aphids, H. defensa is found in several species with an intermediate prevalence and confers protection against parasitoids. In whiteflies, H. defensa is almost fixed in some species of Bemisia tabaci, which suggests an important role of and a transition toward obligate symbiosis. In this study, comparisons of the genome of H. defensa present in two B. tabaci species (Middle East Asia Minor 1 and Mediterranean) and in the aphid Acyrthosiphon pisum revealed that they belong to two distinct clades and underwent specific gene losses. In aphids, it contains highly virulent factors that could allow protection and horizontal transfers. In whiteflies, the genome lost these factors and seems to have a limited ability to acquire genes. However it contains genes that could be involved in the production of essential nutrients, which is consistent with a primordial role for this symbiont. In conclusion, although both lineages of H. defensa have mutualistic interactions with their hosts, their genomes follow distinct evolutionary trajectories that reflect their phenotype and could have important consequences on their evolvability.

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International audience; Many insects harbor inherited bacterial endosymbionts. Although some of them are not strictly essential and are considered facultative, they can be a key to host survival under specific environmental conditions, such as parasitoid attacks, climate changes, or insecticide pressures. The whitefly Bemisia tabaci is at the top of the list of organisms inflicting agricultural damage and outbreaks, and changes in its distribution may be associated to global warming. In this work, we have sequenced and analyzed the genome of Cardinium cBtQ1, a facultative bacterial endosymbiont of B. tabaci and propose that it belongs to a new taxonomic family, which also includes Candidatus Amoebophilus asiaticus and Cardinium cEper1, endosymbionts of amoeba and wasps, respectively. Reconstruction of their last common ancestors' gene contents revealed an initial massive gene loss from the free-living ancestor. This was followed in Cardinium by smaller losses, associated with settlement in arthropods. Some of these losses, affecting cofactor and amino acid biosynthetic encoding genes, took place in Cardinium cBtQ1 after its divergence from the Cardinium cEper1 lineage and were related to its settlement in the whitefly and its endosymbionts. Furthermore, the Cardinium cBtQ1 genome displays a large proportion of transposable elements, which have recently inactivated genes and produced chromosomal rearrangements. The genome also contains a chromosomal duplication and a multicopy plasmid, which harbors several genes putatively associated with gliding motility, as well as two other genes encoding proteins with potential insecticidal activity. As gene amplification is very rare in endosymbionts, an important function of these genes cannot be ruled out.

International audience; The hydraulic properties of the layer at the vicinity of the soil surface have significant impact on evaporation, and could be harnessed to reduce water losses. The effect of the properties of the upper layer on the evolution of phase distribution during the evaporation process is first illustrated from three-dimensional pore network simulations. This effect is then studied from experiments carried out on soil columns under laboratory conditions. Comparisons between homogeneous columns packed with coarse (sand) and fine (sandy loam) materials, and heterogeneous columns packed with layers of fine overlying coarse material and coarse overlying fine material of different thicknesses are performed to assess the impact of upper layer properties on evaporation. Experiments are analyzed using the classical approach based on the numerical solution of Richards's equation and semi-analytical theoretical predictions. The theoretical analysis is based on the clear distinction between two drying regimes, namely the capillary regime and the gravity-capillary regime, which are the prevailing regimes in our experiments. Simple relationships enabling to estimate the duration of stage-1 evaporation (S1) for both regimes are proposed. In particular, this led to defining the characteristic length for the gravity-capillary regime from the consideration of viscous effects at low water content differently from available expressions. The duration of S1, during which most of the water losses occur, for both the homogeneous and two-layer columns are presented and discussed. Finally, the impact of liquid films and it consequences on the soil hydraulic conductivity function are briefly discussed.

International audience; The nucleotide sequence of the helper component protease (HC-Pro) genes of three zucchini yellow mosaic virus (ZYMV) strains has been compared with that of a helper-deficient strain of ZYMV-HC. The comparisons revealed three unique deduced amino acid differences. Two of these mutations were located in regions which are conserved in other potyviruses. The role of these mutations in aphid transmissibility was examined by exchanging DNA fragments of part of the deficient HC-Pro gene with the respective section within the gene of the infectious full-length clone of the aphid-transmissible ZYMV. The first exchange included two of the three mutations, the first coding for a change from Asp to Gly (in a non-conserved region) and the second coding for a change from Arg to Ile [within the Phe-Arg-Asp-Lys (FRNK) conserved box]. This exchange resulted in a reduced transmission (20.6% for the mutated virus compared with 57.4% in the normal ZYMV when acquired from plants and 37.2% compared with 83.1%, respectively, when acquired from membranes). The second exchange incorporated a single mutation [conferring a change from Thr to Ala within the Pro-Thr-Lys (PTK) conserved box]. This single mutation resulted in almost total loss of HC activity in aphid transmission both from plants and from membranes. The Lys residue in the conserved Lys-Ile-Thr-Cys (KITC) box, which is related to loss of HC activity in potato virus Y, tobacco vein mottling virus and in the Michigan strain of ZYMV, is unchanged in the helper-deficient ZYMV. It is therefore proposed that more than one site in HC-Pro may be functionally related to aphid transmissibility. The possible reasons for the role of these mutations in helper activity in aphid transmission of ZYMV are discussed.

Intracellular symbionts of arthropods have diverse influences on their hosts, and their functions generally appear to be associated with their localization within the host. The effect of localization pattern on the role of a particular symbiont cannot normally be tested since the localization pattern within hosts is generally invariant. However, in Israel, the secondary symbiont Rickettsia is unusual in that it presents two distinct localization patterns throughout development and adulthood in its whitefly host, Bemisia tabaci (B biotype). In the "scattered" pattern, Rickettsia is localized throughout the whitefly hemocoel, excluding the bacteriocytes, where the obligate symbiont Portiera aleyrodidarum and some other secondary symbionts are housed. In the "confined" pattern, Rickettsia is restricted to the bacteriocytes. We examined the effects of these patterns on Rickettsia densities, association with other symbionts (Portiera and Hamiltonella defensa inside the bacteriocytes) and on the potential for horizontal transmission to the parasitoid wasp, Eretmocerus mundus, while the wasp larvae are developing within the whitefly nymph. Sequences of four Rickettsia genes were found to be identical for both localization patterns, suggesting that they are closely related strains. However, real-time PCR analysis showed very different dynamics for the two localization types. On the first day post-adult emergence, Rickettsia densities were 21 times higher in the "confined" pattern vs. "scattered" pattern whiteflies. During adulthood, Rickettsia increased in density in the "scattered" pattern whiteflies until it reached the "confined" pattern Rickettsia density on day 21. No correlation between Rickettsia densities and Hamiltonella or Portiera densities were found for either localization pattern. Using FISH technique, we found Rickettsia in the gut of the parasitoid wasps only when they developed on whiteflies with the "scattered" pattern. The results suggest that the localization pattern of a symbiont may influence its dynamics within the host.

International audience; Abstract Bemisia tabaci, an invasive pest that causes crop damage worldwide, is a highly differentiated species complex, divided into biotypes that have mainly been defined based on mitochondrial DNA sequences. Although endosymbionts can potentially induce population differentiation, specialization and indirect selection on mtDNA, studies have largely ignored these influential passengers in B. tabaci, despite as many as seven bacterial endosymbionts have been identified. Here, we investigate the composition of the whole bacterial community in worldwide populations of B. tabaci, together with host genetic differentiation, focusing on the invasive B and Q biotypes. Among 653 individuals studied, more than 95% of them harbour at least one secondary endosymbiont, and multiple infections are very common. In addition, sequence analyses reveal a very high diversity of facultative endosymbionts in B. tabaci, with some bacterial genus being represented by more than one strain. In the B and Q biotypes, nine different strains of bacteria have been identified. The mtDNA-based phylogeny of B. tabaci also reveals a very high nucleotide diversity that partitions the two ITS clades (B and Q) into six CO1 genetic groups. Each genetic group is in linkage disequilibrium with a specific combination of endosymbionts. All together, our results demonstrate the rapid dynamics of the bacterial endosymbiont-host associations at a small evolutionary scale, questioning the role of endosymbiotic communities in the evolution of the Bemisia tabaci species complex and strengthening the need to develop a metacommunity theory of inherited endosymbionts.

Tomato yellow leaf curl virus (TYLCV) ( Geminiviridae : Begomovirus ) is exclusively vectored by the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). TYLCV transmission depends upon a 63-kDa GroEL protein produced by the vector's endosymbiotic bacteria. B. tabaci is a species complex comprising several genetically distinct biotypes that show different secondary-symbiont fauna. In Israel, the B biotype harbors Hamiltonella , and the Q biotype harbors Wolbachia and Arsenophonus. Both biotypes harbor Rickettsia and Portiera (the obligatory primary symbionts). The aim of this study was to determine which B. tabaci symbionts are involved in TYLCV transmission using B. tabaci populations collected in Israel. Virus transmission assays by B. tabaci showed that the B biotype efficiently transmits the virus, while the Q biotype scarcely transmits it. Yeast two-hybrid and protein pulldown assays showed that while the GroEL protein produced by Hamiltonella interacts with TYLCV coat protein, GroEL produced by Rickettsia and Portiera does not. To assess the role of Wolbachia and Arsenophonus GroEL proteins (GroELs), we used an immune capture PCR (IC-PCR) assay, employing in vivo - and in vitro -synthesized GroEL proteins from all symbionts and whitefly artificial feeding through membranes. Interaction between GroEL and TYLCV was found to occur in the B biotype, but not in the Q biotype. This assay further showed that release of virions protected by GroEL occurs adjacent to the primary salivary glands. Taken together, the GroEL protein produced by Hamiltonella (present in the B biotype, but absent in the Q biotype) facilitates TYLCV transmission. The other symbionts from both biotypes do not seem to be involved in transmission of this virus.

International audience; The invertebrate immune system, which has become a major research focus, shares basic features of innate immunity with vertebrates and men. A special feature apparently found only in invertebrates is their close association with vertically heritable symbiotic microorganisms. The validity of the simple view of symbiosis as a mutually beneficial interaction between two uneven partners mainly improving the nutritional state of the two companions has been challenged, however, as symbiotic interactions might involve more partners, and symbiotic functions of the microorganisms are much more diverse than previously assumed. Likewise, microorganisms considered to be mostly harmful to their hosts have been shown to enhance host fitness under some circumstances. The role of a symbiont itself might change between environments or life stages of the host and symbionts might have features previously thought to be specific for pathogens. Understanding symbiotic interactions requires the comprehension of the cross-talk between the symbiotic companions, and the dissection of how long-lasting infections are established without eliminating the symbiont by host immune responses. Fascinating new findings in this field revealed that symbiosis might contribute to defence against pathogens or natural enemies. New symbiont-based approaches to defeat agricultural pests or pathogen transmission by arthropod vectors are becoming conceivable.

International audience

Zucchini yellow mosaic virus (ZYMV, Potyvirus) is a very damaging cucurbit virus worldwide. Interspecific crosses with resistant Cucurbita moschata have led to the release of “resistant” zucchini squash (C. pepo) F1 hybrids. However, although the resistance is almost complete in C. moschata, the commercial C. pepo hybrids are only tolerant. ZYMV evolution toward increased aggressiveness on tolerant hybrids was observed in the field and was obtained experimentally. Sequence comparisons and recombination experiments revealed that a point mutation in the P3 protein of ZYMV was enough to induce tolerance breaking. Competition experiments were performed between quasi-isogenic wild-type, and aggressive variants of ZYMV distinguished by monoclonal antibodies. The aggressive mutants were more fit than wild-type strains in mixed infections of tolerant zucchini, but they presented a drastic fitness loss in mixed infections of susceptible zucchini or melon. Thus, the ability to induce severe symptoms in tolerant zucchini is related to a genetic load in susceptible zucchini, but also on other susceptible hosts. This represents the first quantitative study of the fitness cost associated with tolerance breaking for a plant virus. Thus, although easily broken, the tolerance might prove durable in some conditions if the aggressive variants are counterselected in susceptible crops.

The genome of “ Candidatus Portiera aleyrodidarum,” the primary endosymbiont of the whitefly Bemisia tabaci (Mediterranean species), is reported. It presents a reduced genome (357 kb) encoding the capability to synthetize, or participate in the synthesis of, several amino acids and carotenoids, being the first insect endosymbiont capable of supplying carotenoids.

International audience

* INRA Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9; International audience

7. EUCARPIA Meeting on Cucurbit Genetics and Breeding, 2000/03/19-23, 2000, Ma'ale Ha Hamisha, Israël; International audience; Zucchini yellow mosaic potyvirus (ZYMV) is probably one of the best examples of emerging aphid-transferred plant viruses. Reported in 1981 in Italy, it was within less than 10 years found in most of the cucurbit growing areas in the world, most often associated with very severe yield losses. Cross-protection involves a mild virus strain (“protecting strain”) and a wild-type strain (“challenging strains”). Commercial treatment against the virulent virus in cucurbits is carried out by mechanical inoculation of the mild natural virus into the plant. In the last five years in Israel, efficient implementation on a large scale of natural mild virus (ZYMV-WK) by cross-protection has been performed. A unique technology was developed for inoculating of the mild virus into seedlings in the nursery. Starting with field experiments in 1992, during the years 1996–9 over 2500 ha were treated. In order to facilitate a worldwide system for operation of cross-protection and to minimize the risks involved in its use, an ideal protective strain should have several characteristics and successful operation is dependent on three essential elements.

International audience; This chapter focuses on the epidemiological risks from mixed virus infections and transgenic plants expressing viral genes. Several types of interaction may occur between a virus infecting a transgenic plant and either the transgene transcript or its translation product. These include heterologous encapsidation or interaction with a transmission accessory factor, which have the potential to alter vector specificity; complementation from a protein involved in cell-to-cell or long-distance movement, with possible effects on tissue tropism or the ability to establish a systemic infection; synergism resulting in increased replication and/or increased symptom severity; and recombination resulting in gain of function or alteration of pathogenicity. The chapter reviews the general aspects of vector specificity in different virus groups, as this could be altered either by recombination or by virus–transgene interactions. Potential complementation in a transgenic plant would also be limited in epidemiological effect, as the complementing transgene would not be present in nontransgenic plants. The chapter also discusses various means of minimizing the perceived risks of interactions between viruses and transgenically expressed viral sequences and the potential benefits to be gained from virus-resistant transgenic plants in comparison to the perceived risks.

International audience; Aphid transmission of a non-aphid-transmissible strain of zucchini yellow mosaic virus (ZYMV-NAT) occurs in transgenic plants expressing the plum pox potyvirus (PPV) coat protein (CP) gene. Heteroencapsidation has been shown to be responsible for this modification in the epidemiological characteristics of the infecting virus. In order to prevent this biological risk, several modified PPV CP constructs were produced that were designed to interfere with heteroencapsidation itself or to block aphid transmission of heteroencapsidated virions, These constructs were first expressed in Escherichia coli in order to check for the accumulation of pseudo-particles by electron microscopy, Virus-like particles (VLPs) were found with the full-length CP and with a PPV CP lacking the DAG amino acid triplet involved in aphid transmission. However, no VLPs were observed with CP lacking R-220, Q(221) or D-264, amino acids known to be essential for the assembly of other potyvirus CPs. Transgenic Nicotiana benthamiana lines expressing the different PPV CP constructs were infected with ZYMV-NAT. Aphid transmission assays performed with these plants demonstrated that the strategies developed here provide an effective means of minimizing the biological risks associated with heteroencapsidation.

International audience

International audience; Monoclonal antibodies (MAbs) raised against the coat protein of zucchini yellow mosaic potyvirus (ZYMV) were characterized by epitope mapping using synthetic oligopeptides. Two mutant viruses with a mutation in the amino acid sequence important for epitope recognition in vitro were obtained by site-directed mutagenesis of a full-length cDNA of ZYMV. Two MAbs, CC11 and DD2, could distinguish specifically between these mutants in mixed infections, or after sequential inoculations of muskmelons. Sequential inoculations of the mutants and analysis with MAbs CC11 and DD2 revealed that cross-protection was established between these quasi-isogenic strains within 48 h.

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International audience; Transgenic Nicotiana benthamiana plants expressing the coat protein of an aphid-transmissible strain of plum pox potyvirus (PPV) were infected by a non-aphid-transmissible strain of zucchini yellow mosaic potyvirus (ZYMV-NAT) in which the coat protein has a D-T-G amino acid triplet instead of the D-A-G triplet essential for aphid transmission. The aphid vector Myzus persicae could acquire and transmit ZYMV-NAT from these plants but not from infected N. benthamiana control plants that were not transformed or that were transformed but not expressing the PPV coat protein. The aphid-transmitted ZYMV subcultures were shown still to be non-aphid-transmissible from plants not expressing PPV coat protein, which indicated that their transmission was not due to RNA recombination or to reversion to the aphid-transmissible type. In immunosorbent electron microscopy experiments using the decoration technique, virus particles in the infected control plants could be coated only with ZYMV antibodies, while virus particles in the infected transgenic plants expressing the PPV coat protein could be coated not only with ZYMV antibodies but also in part with PPV antibodies. This suggests that aphid transmission of ZYMV-NAT occurred through heterologous encapsidation. These results indicate a potential risk of releasing genetically engineered plants into the environment.

International audience

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International audience; Two isolates of zucchini yellow mosaic virus (ZYMV) were found to be either highly (HAT) or poorly (PAT) aphid-transmissible. The inefficient transmission of ZYMV-PAT was independent of the virus source plant or aphid species used. The ZYMV-PAT and ZYMV-HAT, from which the former was derived, did not differ in their host range or serological properties. Purified virions of either ZYMV-HAT or ZYMV-PAT were readily transmitted by aphids when crude or concentrated helper component (HC) from ZYMV-HAT was provided, but were not transmitted when mixed with crude or concentrated HC from ZYMV-PAT. It is concluded that ZYMV-PAT HC is responsible for the defect in aphid transmissibility of this isolate. However a component serologically related to HC was detected both in ZYMV-PAT-infected plants or in ZYMV-PAT RNA in vitro translation products, indicating that an ineffective form of HC is produced by ZYMV-PAT. Furthermore, in in vitro acquisition experiments conducted with ZYMV-PAT and a non-aphid-transmissible isolate (ZYMV-NAT) deficient in the coat protein, high levels of transmission were observed only in the combination containing purified virions of ZYMV-PAT and HC from ZYMV-NAT. This provided additional proof for the deficiencies in the HC for ZYMV-PAT and in the coat protein for ZYMV-NAT.

International audience; This paper presents the over-arching latest advances of the multi-actor approach project, TechCare, which aims at developing appropriate early warning systems and business models using innovative technologies to improve welfaremanagement in EU small ruminant production systems. Small ruminants play a key socio-economic role in Europe, especially in harsh environments where innovative technology is not yet commonly adopted. Small ruminants are oftenmanaged as a flock/herd, allowing only average welfare states to be considered. Innovative technologies are a unique opportunity to improve small ruminant welfare management at the individual or flock/herd level, along the valuechain. To this aim, in each participant country, stakeholders will be involved to prioritize the most relevant welfare issues and corresponding indicators. In a second step, they will contribute to assess an array of country and productionsystem-tailored innovative technologies and early warning systems with potential for managing the prioritized welfare issues. These will then be tested on pilot farms in different conditions and validated at large-scale. The best performingtechnologies and systems which successfully pass all these steps will be evaluated for their viability in terms of business models. Whilst other consortium authors will present details of specific project activities (namely – stakeholders’engagement, welfare challenges identification and innovative technologies inventory), this paper focus on presenting preliminary activities and goals of the project to ensure awareness to a wide range of small ruminant stakeholders.