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International audience; The One Health approach to understanding disease epidemiology and achieving surveillance and prevention is holistic all while focusing on zoonotic diseases. Many of its principles are similar to those espoused in Agroecology, begetting the question of what One Health can contribute - in practice - to preventing plant disease. Here we describe four knowledge challenges for plant health management that have arisen from the One Health experience for zoonotic diseases that could boost prospects for novel approaches to plant disease surveillance, prediction and prevention. The challenges are to i) uncover reservoirs and revise pathogen life histories, ii) elucidate drivers of virulence beyond the context of direct host-pathogen interactions, iii) account for the natural highways of long distance dissemination (i.e., surface water and air mass movement), and iv) update disease forecasts in the face of changing land use, cultivation practices and climate. Furthermore, we note that implementation of a One Health approach to disease surveillance and prevention will require mobilization of tools to deal with the representation and accessibility of massive and heterogeneous data and knowledge; with knowledge inference, data science, modelling, and pattern recognition; and multi-actor approaches that unite different sectors of society as well as different scientific disciplines. The infrastructure to build and the obstacles to overcome for a bona fide One Health approach to disease surveillance and prevention are the key commonalities where actors in the efforts to prevent zoonotic diseases and plant disease can work together for human, animal and plant health and sustainable management of biodiversity.

Determining how reproductive barriers modulate gene flow between populations represents a major step toward understanding the factors shaping the course of speciation. Although many indices quantifying reproductive isolation (RI) have been proposed, they do not permit the quantification of cross-direction-specific RI under varying species frequencies and over arbitrary sequences of barriers. Furthermore, techniques quantifying associated uncertainties are lacking, and statistical methods unrelated to biological process are still preferred for obtaining confidence intervals and P-values. To address these shortcomings, we provide new RI indices that model changes in gene flow for both directions of hybridization, and we implement them in a Bayesian model. We use this model to quantify RI between two species of the psyllid Cacopsylla pruni based on field genotypic data for mating individuals, inseminated spermatophores and progeny. The results showed that preinsemination isolation was strong, mildly asymmetric, and indistinguishably different between study sites despite large differences in species frequencies; that postinsemination isolation strongly affected the more common hybrid type; and that cumulative isolation was close to complete. In the light of these results, we discuss how these developments can strengthen comparative RI studies.

Alfalfa leaf curl virus (ALCV) is the first geminivirus for which aphid transmission was reported. Transmission byAphis craccivorawas determined previously to be highly specific and circulative. Using various complementary techniques, the transmission journey of ALCV was monitored from its uptake from infected plant tissues up to the head of its vector. ALCV was shown to be restricted to phloem tissues using fluorescencein situhybridization (FISH) and electropenetrography (EPG) monitoring of virus acquisition. Furthermore, the virus is heterogeneously distributed in phloem tissues, as revealed by FISH and quantitative PCR of viral DNA acquired by EPG-monitored aphids. Despite the efficient ingestion of viral DNA, about 106viral DNA copies per insect in a 15 h feeding period on ALCV-infected plants, the individual maximum transmission rate was 12 %. Transmission success was related to a critical viral accumulation, around 1.6×107viral DNA copies per insect, a threshold that generally needed more than 48 h to be reached. Moreover, whereas the amount of acquired virus did not decrease over time in the whole aphid body, it declined in the haemolymph and heads. ALCV was not detected in progenies of viruliferous aphids and did not affect aphid fitness. Compared to geminiviruses transmitted by whiteflies or leafhoppers, or to luteoviruses transmitted by aphids, the transmission efficiency of ALCV byA. craccivorais low. This result is discussed in relation to the aphid vector of this geminivirus and the agroecological features of alfalfa, a hardy perennial host plant.

Two members of the genus Capulavirus (Geminiviridae) are transmitted by aphids including Alfalfa leaf curl virus (ALCV) transmitted by Aphis craccivora. The capulavirus Euphorbia caput-medusae latent virus was shown here to be transmitted also by A. craccivora, using the population EuphorbiaSA. ALCV was transmissible by several A. craccivora populations including Robinia, but not EuphorbiaSA, reflecting a high transmission specificity. ALCV accumulation and localization were analyzed in whole insects, midguts, hemolymphs, and heads of aphids from both populations and from the non-vector species Acyrthosiphon pisum. A 6-day persistence was observed in A. craccivora populations but not in A. pisum. Vector and non-vector A. craccivora populations could be distinguished by contrasted virus accumulations and midgut intracellular localization. Results confirm that ALCV is transmitted according to a circulative-persistent mode, and are consistent with a gut barrier to the transmission of ALCV in A. pisum and a primary salivary gland barrier in A. craccivora.

BGPI : équipe 6; International audience; ‘Candidatus Phytoplasma’ species are mostly transmitted from plant to plant by phloem feeding hemipterans, primarily leafhoppers (Cicadellidae) and planthoppers (Fulgoroidea) (Hemiptera, Auchenorrhyncha). However, there is one group of phytoplasmas, the 16SrX or apple proliferation group, whose members are transmitted by psyllid vectors of the superfamily Psylloidea (Hemiptera, Sternorrhyncha). These psyllid-transmitted phytoplasmas are genetically closely related and are associated with economically important diseases of fruit trees such as pear decline, apple proliferation and European stone fruit yellows. The psyllid vector species of these phytoplasmas are also closely related and all belong to the genus Cacopsylla. Both, phytoplasmas and psyllid vectors, are geographically limited to the Palaearctic region, mainly Europe. Only pear decline and peach yellow leaf roll phytoplasmas have probably been introduced to America along with their vectors. As phytoplasma-infected trees cannot be cured and resistant plant material is not available to the growers, preventive control measures such as vector control are of paramount importance to limit the spread of these diseases. Thus, detailed knowledge about the biology and ecology of the vector species, their host plants as well as knowledge about the transmission parameters is crucial.

Single-stranded DNA (ssDNA) plant viruses belong to the families Geminiviridae and Nanoviridae. They are transmitted by Hemipteran insects in a circulative, mostly non-propagative, manner. While geminiviruses are transmitted by leafhoppers, treehoppers, whiteflies and aphids, nanoviruses are transmitted exclusively by aphids. Circulative transmission involves complex virus&ndash, vector interactions in which epithelial cells have to be crossed and defense mechanisms counteracted. Vector taxa are considered a relevant taxonomic criterion for virus classification, indicating that viruses can evolve specific interactions with their vectors. Thus, we predicted that, although nanoviruses and geminiviruses represent related viral families, they have evolved distinct interactions with their vector. This prediction is also supported by the non-structural Nuclear Shuttle Protein (NSP) that is involved in vector transmission in nanoviruses but has no similar function in geminiviruses. Thanks to the recent discovery of aphid-transmitted geminiviruses, this prediction could be tested for the geminivirus alfalfa leaf curl virus (ALCV) and the nanovirus faba bean necrotic stunt virus (FBNSV) in their common vector, Aphis craccivora. Estimations of viral load in midgut and head of aphids, precise localization of viral DNA in cells of insect vectors and host plants, and virus transmission tests revealed that the pathway of the two viruses across the body of their common vector differs both quantitatively and qualitatively.

Flowers are a remarkable component of everyday life. Their diversity of shape, colour and fragrance witnesses the importance of the joint evolutionary processes resulting from the interactions between plants and their insect pollinators. Indeed, pollination mutualisms with insects are key factors that have allowed the evolutionary success and diversification of flowering plants (McKey & Hossaert-McKey, 2008). This diversification of plants has led to an even more impressive diversification of insects. This chapter retraces the main steps of the past history of diversification of pollination interactions with the emergence of some major pollinator groups of insects and proposes some insights into the selective processes acting on the evolution of the entomophilous pollination.

International audience; Concanavalin A (lectin from Canavalia ensiformis L., ConA) has previously been shown to act as a feeding inhibitor for Acyrthosiphon pisum, the pea aphid. In the present study a range of histochemical and biochemical techniques were used to elucidate the target tissues and binding sites of the lectin in the aphid. Diet uptake was evaluated using a radioactive tracer (14C-methylated inulin) and demonstrated that adults were capable of ingesting high quantities of the toxin (approx. 1 microg over a 48 h period). Electophoretic analysis and enzyme-linked immuno-sorbent assay of honeydew samples confirmed these results and further demonstrated that only small levels of ConA were excreted. Histofluorescence and immunolocalisation studies on nymphs revealed that the stomach was the primary target for ConA. At concentrations up to 400 microg ml(-1), lectin binding only occurred in the stomach region, however, at high concentrations (800 microg ml(-1)) the whole digestive tract was stained, although there was no evidence of binding in either the oesophagus or rectum. In addition to binding, there was evidence to suggest that ConA was also causing systemic effects in that the lectin appeared to cross the intestinal epithelial barrier. Immunohistochemical and electron microscopy studies revealed that ConA induced severe cellular swelling of the epithelial cells, accompanied by hypersecretion and a progressive detachment of the apical membrane; however, the striated border itself did not appear to be directly affected. Furthermore, there was no lysis of the epithelium, nor loss of integrity of the epithelial cells themselves. Our results suggest that ConA interacts with glycosylated receptors at the surface of the stomach epithelial cells, interfering with normal metabolism and cell function, resulting in a rapid feedback response on feeding behaviour. Whilst our results provide a much greater understanding regarding the modes of action of ConA in insects, they suggest that different lectins, including other mannose binding lectins, have different modes of action at the cellular levels, and thus generalizations should be treated with caution.

Potato plants (Solanum tuberosum) cv. Desiree were transformed with the genes encoding the proteins bean chitinase (BCH), snowdrop lectin (GNA) and wheat α-amylase inhibitor (WAI) under the control of the constitutive CaMV 35S promoter. Transgenic plants with detectable levels of foreign RNA were then selected for further characterisation with respect to protein expression levels by immunodot blot analysis using polyclonal antibodies raised against the respective protein. With the exception of WAI, plants expressing high levels of RNA, expressed correspondingly high levels of the foreign protein (1.5–2.0% of the total soluble protein). Although high levels of WAI mRNA were detected in some of the transformants, the protein could not be detected. On the bases of expression levels, two lines, designated PWG6#85 (transformed with the double construct WAI/GNA) and PBG6#47 (transformed with the double construct BCH/GNA), were selected for testing in aphid trials for enhanced levels of resistance. Both transgenic lines had a marked and significant effect on fecundity. The number of nymphs produced per female per day peaked at 4.1 and 4.2 for lines PBG6#47 and PWG6#85 respectively, compared to a value of 5.4 on control plants. Total nymphal production was also significantly lower on either of the transgenic lines compared to control plants (P

Three mannose-binding lectins were assayed in artificial diets for their toxic and growth-inhibitory effects on nymphal development of the peach-potato aphid Myzus persicae. The snowdrop (Galanthus nivalis) lectin GNA was the most toxic, with an induced nymphal mortality of 42% at 1500 μg ml -1 (30 μM) and an IC 50 (50% growth inhibition) of 630 μg ml -1 (13 μM). The daffodil (Narcissus pseudonarcissus) lectin NPA and a garlic (Allium sativum) lectin ASA induced no significant mortality in the range 10-1500 μg ml -1 , but did result in growth inhibition of 59% (NPA) and 26% (ASA) at 1500 μg ml -1 (40 μM for NPA, 63 μM for ASA). All three lectins were responsible for a slight but significant growth stimulation when ingested at 10 μg ml -1 , reaching + 26%, + 18% and + 11% over the control values for the garlic lectin, the daffodil lectin and the snowdrop lectin, respectively. GNA, as well as the glucose/mannose binding lectin Concanavalin A, were also provided at sublethal doses throughout the life cycle of the aphids, and effects on adult performance were monitored. Adult survival was not significantly altered, but both lectins adversely affected total fecundity and the dynamics of reproduction, resulting in significant reduction in calculated r m's (population intrinsic rate of natural increase) on lectin-containing diets. These effects are discussed in relation to the use of transgenic plants expressing these toxic lectins for potential control of aphid populations.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; Aphis gossypii and Bemisia tabaci are severe hemipteran pests of melon crops and breeding for resistance to both insects is required to reduce pesticide use. Resistance was evaluated for its effect on behaviour and biotic potential of both hemipterans in a population of recombinant inbred lines (RILs) derived from the cross Védrantais x PI 161375. Insect variability was considered using two A. gossypii clones and two B. tabaci populations. Two additive QTLs affected the whiteflies. Four additive QTLs and two couples of epistatic QTLs affected the aphids. Amongst them, a major QTL affects both behaviour and biotic potential of A. gossypii and therefore a same R gene induces both antixenosis and antibiosis. This major QTL colocalizes with the Vat gene belonging to the NBS-LRR gene family. No loci affected both aphids and whiteflies contrary to what was observed for the Mi1.2 gene, a NBSLRR gene in tomato. Original populations with different allelic compositions at QTLs affecting A. gossypii were built by one inter-crossing of RILs used for the mapping process. The genetic background was shown homogeneous between these populations what allowed validating QTLs and investigating the effect of allelic combinations at QTLs. Effects of QTLs were stronger than expected and some QTLs had a wider spectrum than expected. This strategy of validation appeared rapid and low cost.

UMR BGPI - Equipe 6; UMR CBGPPublication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; Cacopsylla pruni is the vector of European stone fruit yellows, a quarantine disease of Prunus trees. Nine polymorphic microsatellite markers were developed from enriched DNA libraries. Allelic variability was assessed in a collection of 149 females obtained from five localities covering a large geographical area in France. The number of detected alleles ranged from 8 to 37. Within the localities, observed and expected heterozygosities averaged across loci ranged from 0.39 to 0.55, and from 0.68 to 0.81, respectively. A heterozygote deficiency was detected for almost all loci, possibly due to a high null allele frequency. Other possible causes of the homozygote excess (mode of reproduction, inbreeding, assortative mating or Wahlund effect) are discussed. These variable microsatellite loci can provide tools to assess overall genetic variation in this important vector species. They will be used to search for population structure and migration patterns of C. pruni.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; European stone fruit yellows (ESFY) is becoming a major economic problem for Prunus growers in Europe. The causal agent ("Candidatus Phytoplasma prunorum") and its vector (Cacopsylla pruni) have been identified, but the present knowledge of the risk factors for this disease relies, at best, on specific experiments. To assess the relative significance of several factors correlated with ESFY incidence in the field, an exhaustive survey was performed on apricot and Japanese plum orchards in the Crau plain (France). After a preliminary multivariate exploration of the data, we used a logistic regression model to analyze and predict the cumulative number of diseased trees on the basis of a set of quantitative (age, planting density, and area of the orchard) and categorical variables (species, cultivar, and rootstock). Because of the nature of the data, we used an overdispersed binomial model and we developed a parametric bootstrap procedure based on the beta-binomial distribution to obtain confidence intervals. Our results indicated that the age, species, and cultivar of the scion were the major factors explaining the observed number of diseased trees. The planting density and the rootstocks used in the zone under study were less significant, and the area of the orchard had no effect. The residuals of the model showed that some explanatory variables had not been taken into account, because part of the remaining variability could be explained by a grower effect. The spatial distribution of the residuals suggested that one of the reasons for this grower effect was the correlation between orchards closer than 100 m, possibly caused by the flight behavior of infectious vectors.

Acute toxicity of thirty lectins was tested against the pea aphid Acyrthosiphon pisum (Harris) (Homoptera, Aphididae: Macrosiphini). Activity was measured on artificial diets containing moderate concentrations of lectins (10–250 μg/ml) by scoring mortality and growth inhibition over the whole nymphal period (7 days at 20°C). Most of the proteins tested exhibited low toxicity, but some induced significant mortality; these included the lectins from jackbean (Concanavalin A), amaranth, lentil and snowdrop. There was no direct correlation between toxicity and sugar specificity of the lectin; however, many mannose-binding lectins were toxic towards A. pisum. Concanavalin A was also tested on five other aphid species (Aphis gossypii, Aulacortum solani, Macrosiphum euphorbiae, Macrosiphum albifrons and Myzus persicae) at concentrations between 10–1500 μg/ml. Mortality was very variable from one species to another. Strong growth inhibition invariably occurred within this concentration range, although dose-response curves differed substantially between aphid species. The peptidase complement of A. pisum's digestive tract was also investigated, as well as the oral toxicity of some protease inhibitors (PIs) to this aphid. Most protein PIs were inactive, and no part of the digestive tract contained detectable amounts of endo-protease activity. This is in contrast to the strong amino-peptidase activity which was shown to occur predominantly in the midgut and crop portions of the digestive tract. The potential of lectins in transgenic crops to confer Host-Plant Resistance to aphids is discussed.

Mannose-binding lectins were shown to be useful in creating transgenic plants resistant to insects, including many phloem-feeding Hemiptera. Before these plants can be used extensively, it is important to understand how these lectins exert their toxic effects on the target organisms. We investigated the feeding alterations induced by presenting the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), with a diet containing the lectin from Canavalia ensiformis (ConA). A series of behavioural experiments were carried out to detect potential sensory mediation of lectin activity. Choice tests performed with a 400 μg ml -1 conA diet (3.7 μM of native tetramer) showed that A. pisum quickly rejected the ConA diet, but that this reaction was not typical of a sensory-mediated phagodeterrent effect. In addition, the aphids did not develop a conditioned taste aversion to the lectin. Diet uptake was evaluated using a radioactive tracer ( 14 C-methylated inulin), and showed depression of ingestion only after 16 h at 200 μg ml -1 or after 8 h at 400 μg ml -1 ConA. This effect was reversible under our test conditions. No evidence was obtained for early detection of the lectin, even by intoxicated aphids. An electrical penetration graph technique was adapted to artificial diets and provided short-term continuous analysis on feeding/probing events. At the 400 μg ml -1 level, adults were affected and had reduced ingestion durations as early as in the first 4 h of contact, but experienced an adaptation to the behavioural alterations induced by lectin feeding. Overall, feeding deterrency following exposure to mannose lectins appeared to be a consequence of intoxication, and not due to a sensory mediated process.

International audience; There is growing evidence that microorganisms are important ‘hidden players’ in insect–plant interactions. Insect symbionts can directly affect these interactions by providing insects with key nutrients or by interfering with the plant to modulate food provisioning to insects and plant defences. Insect symbionts can also have indirect cascading ecological consequences at the community level through insect- and plant-mediated effects that include their impact on insect reproduction, on natural enemies of herbivores or on plant-associated microorganisms. Identification of symbiotic communities associated with insects, characterization of transmission and acquisition patterns as well as understanding of molecular mechanisms underlying these plant–insect–microbe interactions have important ecological and evolutionary consequences. This review highlights the excitement that surrounds these investigations and the promise they hold for a better understanding of the functional, ecological and evolutionary impacts of symbionts on plant–insect interactions, with implications and relevance for both applied and fundamental researches.