Plant infection by two different viruses induce contrasting changes of vectors fitness and behavior

Abstract Insect-vectored plant viruses can induce changes in plant phenotypes, thus influencing plant?vector interactions in a way that may promote their dispersal according to their mode of transmission (i.e., circulative vs. noncirculative). This indirect vector manipulation requires host?virus?vector coevolution and would thus be effective solely in very specific plant?virus?vector species associations. Some studies suggest this manipulation may depend on multiple factors relative to various intrinsic characteristics of vectors such as transmission efficiency. In anintegrative study, we tested the effects of infection of the Brassicaceae Camelina sativa with the noncirculative Cauliflower mosaic virus (CaMV) or the circulative Turnip yellows virus (TuYV) on the host-plant colonization of two aphid species differing in their virus transmission efficiency: the polyphagous Myzus persicae, efficient vector of both viruses, and the Brassicaceae specialist Brevicoryne brassicae, poor vector of TuYV and efficient vector of CaMV. Results confirmed the important role of virus mode of transmission as plant-mediated effects of CaMV on the two aphid species induced negative alterations of feeding behavior (i.e., decreased phloem sap ingestion) and performance that were both conducive for virus fitness by promoting dispersion after a rapid acquisition. In addition, virus transmission efficiency may also play a role in vector manipulation by viruses as only the responses of the efficient vector to plant-mediated effects of TuYV, that is, enhanced feeding behavior and performances, were favorable to their acquisition and further dispersal. Altogether, this work demonstrated that vector transmission efficiency also has to be considered when studying the mechanisms underlying vector manipulation by viruses. Our results also reinforce the idea that vector manipulation requires coevolution between plant, virus and vector

Probing Behavior of Apterous and Alate Morphs of two Potato—Colonizing Aphids

Secondary host plant colonization by aphids involves alate and apterous morphs to spread in the population at a large scale by flying or, at a finer one, by walking. Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae) and Myzus persicae Sulzer (Hemiptera: Aphididae) are two polyphagous aphids that cause serious losses on many crops, particularly on potato, Solanum tuberosum L. (Solanales: Solanaceae). When settlement of virginoparous alate aphids occurs, apterous individuals are produced and spread within the potato field. As these two potato colonizers originate from different areas and show different body length, this study compared probing behaviors of virginoparous alate and apterous M. persicae and M. euphorbiae on one of their secondary host plants, Solanum tuberosum. Non—choice bioassays and electrical penetration graph (EPG) recordings were performed. Most M. euphorbiae of the two morphs rapidly accepted potato plants and exhibited long duration of probing, phloem sap salivation, and ingestion phases. In contrast, at the end of the experiment, most alates of M. persicae left the potato leaflet after brief gustative probes. Moreover, EPG experiments showed that the main difference between both morphs of the two species concerned the xylem ingestion parameter. Differences between species were also reported, such as an increased total duration of probing in both morphs and enhanced phloem ingestion duration in apterous M. euphorbiae. All the differences highlighted in this study are discussed according to the variations observed in aphid body size and to their historical association with Solanum species

Essential Oil Trunk Injection Into Orchard Trees: Consequences on the Performance and Preference of Hemipteran Pests.

peer reviewedApples and pears are among the most widely cultivated fruit species in the world. Pesticides are commonly applied using ground sprayers in conventional orchards; however, most of it will not reach the target plant, increasing the contamination of nontarget organisms such as natural predators, pollinators, and decomposers. Trunk injection is an alternative method of pesticide application that could reduce risks to beneficials and workers. Essential oils represent a 'green' alternative to pesticides due to their reported insecticidal, antimicrobial, antiviral, nematicidal, and antifungal properties. The aim of this study was, therefore, to evaluate the impact that the injection of a cinnamon essential oil solution into the trunk of apple and pear trees could have on their respective pests, Dysaphis plantaginea and Cacopsylla pyri, respectively. The feeding behavior (preference), the life history traits (performance), and the timing of this effect were measured. The injection of an essential oil emulsion in trees impacted hemipteran host-plant colonization, as for both species a modification of their preference and of their performance was observed. The feeding behavior of D. plantaginea was altered as a significantly lower proportion of aphids ingested phloem sap on injected trees, suggesting that the aphids starved to death. On the contrary, the feeding behavior of the psyllids was little changed compared to the control condition, implying that the observed mortality was due to intoxication. The results presented here could theoretically be used to control these two orchard hemipteran pests, although the effectiveness in real conditions still has to be demonstrated

Virus effects on plant quality and vector behavior are species specific and do not depend on host physiological phenotype

There is growing evidence that plant viruses manipulate host plants to increase transmission-conducive behaviors by vectors. Reports of this phenomenon frequently include only highly susceptible, domesticated annual plants as hosts, which constrains our ability to determine whether virus effects are a component of an adaptive strategy on the part of the pathogen or simply by-products of pathology. Here, we tested the hypothesis that transmission-conducive effects of a virus (Turnip yellows virus [TuYV]) on host palatability and vector behavior (Myzus persicae) are linked with host plant tolerance and physiological phenotype. Our study system consisted of a cultivated crop, false flax (Camelina sativa) (Brassicales: Brassicaceae), a wild congener (C. microcarpa), and a viable F1 hybrid of these two species. We found that the most tolerant host (C. microcarpa) exhibited the most transmission-conducive changes in phenotype relative to mock-inoculated healthy plants: Aphids preferred to settle and feed on TuYV-infected C. microcarpa and did not experience fitness changes due to infection—both of which will increase viruliferous aphid numbers. In contrast, TuYV induced transmission-limiting phenotypes in the least tolerant host (C. sativa) and to a greater degree in the F1 hybrid, which exhibited intermediate tolerance to infection. Our results provide no evidence that virus effects track with infection tolerance or physiological phenotype. Instead, vector preferences and performance are driven by host-specific changes in carbohydrates under TuYV infection. These results provide evidence that induction of transmission-enhancing phenotypes by plant viruses is not simply a by-product of general pathology, as has been proposed as an explanation for putative instances of parasite manipulation by viruses and many other taxa

Oddity in diel periodicity of Ditula angustiorana (Haw.) (Lepidoptera: Torticidae) female calling behaviour, pheromone titre and reproductive activity

The diel periodicity of female calling behaviour in Ditula angustiorana (Haw.) was studied under laboratory conditions. Observations throughout photophases and scotophases showed that D. angustiorana females presented a rare diurnal calling behaviour with two distinct calling periods, one at the first part of the photophase (L+5) and another one at the end (L+14). Mating only occurred during the second calling period (L+14). Five components were identified in extracts of the pheromone glands: Z10-14:Ac, 14:Ac, Z10-14:OH, Z8-14:Ac, Z8-14:OH in the average ratio of 74.1/18.2/4.8/2.2/0.6 respectively. The blend ratio remains similar throughout the photoperiod, whilst the total quantity of pheromone components reached a maximum during the calling period overlapping the mating period (L+14). Wind tunnel experiment confirms that the synthetic blend baited with the identified pheromone components was as attractive as calling females for males. The particular chemical structure of the components within Tortricidae and the particular occurrence of the two calling periods, one not matching any reproductive behaviour are discussed in terms of phylogeny and sexual selection

Utilisation des médiateurs chimiques volatils en protection des cultures

chapitre 42National audienc

Cascading effects of N input on tritrophic (plant-aphid-parasitoid) interactions

International audienceBecause N is frequently the most limiting mineral macronutrient for plants in terrestrial ecosystems, modulating N input may have ecological consequences through trophic levels. Thus, in agro-ecosystems, the success of natural enemies may depend not only from their herbivorous hosts but also from the host plant whose qualities may be modulated by N input. We manipulated foliar N concentrations by providing to Camelina sativa plants three different nitrogen rates (control, optimal, and excessive). We examined how the altered host-plant nutritional quality influenced the performances of two aphid species, the generalist green peach aphid, Myzus persicae, and the specialist cabbage aphid, Brevicoryne brassicae, and their common parasitoid Diaeretiella rapae. Both N inputs led to increased N concentrations in the plants but induced contrasted concentrations within aphid bodies depending on the species. Compared to the control, plant biomass increased when receiving the optimal N treatment but decreased under the excessive treatment. Performances of M.persicae improved under the optimal treatment compared to the control and excessive treatments whereas B.brassicae parameters declined following the excessive N treatment. In no-choice trials, emergence rates of D.rapae developing in M.persicae were higher on both optimum and excessive N treatments, whereas they remained stable whatever the treatment when developing in B.brassicae. Size of emerging D.rapae females was positively affected by the treatment only when it developed in M.persicae on the excessive N treatment. This work showed that contrary to an optimal N treatment, when N was delivered in excess, plant suitability was reduced and consequently affected negatively aphid parameters. Surprisingly, these negative effects resulted in no or positive consequences on parasitoid parameters, suggesting a buffered effect at the third trophic level. Host N content, host suitability, and dietary specialization appear to be major factors explaining the functioning of our studied system

Interactions between phytovirus and aphids vectors can be modulated depending on vector transmission efficiency

National audienceVector-borne viruses can induce changes in the phenotype of their host plants that may in turninfluence the frequency and nature of host–vector interactions Manipulation of vectorbehaviour by phytoviruses usually facilitates their propagation and seems to convergeaccording to the virus transmission mode. However, to our knowledge, this convergence hasnever been related to the vector transmission efficiency. We investigated the effects ofinfection of Camelina sativa by the persistent Turnip Yellows Virus and the semi-persistentCauliflower Mosaic Virus on (i) arrestment and dispersal, (ii) feeding behaviour (usingelectropenetrography) and (iii) physiology of two aphid species: the polyphagous Myzuspersicae and the Brassicaceae specialist Brevicoryne brassicae. Results showed TuYV-infectedcamelina induced positive effects on the feeding behaviour and physiology of Myzus persicae,a vector with high transmission efficiency; but induced negative effects on Brevicorynebrassicae, a poor vector of TuYV. CaMV-infected plants had similar effects on both aphidspecies showing equivalent transmission efficiency for this virus. In conclusion, viralmanipulation of vector behaviour is likely to depend not only on the virus mode oftransmission, which is generally considered as a common assumption, but also on the aphidtransmission efficiency

Vector manipulation by viruses: The pathosystem Brassicaceae-aphids-phytoviruses, a study case

International audienceIntroduction: Vector-borne viruses can induce changes in the phenotype of their host plants that influence the frequency and nature of host–vector interactions. Insect-vectored phytoviruses that differ in their modes of transmission (persistent, semi-persistent and non-persistent) benefit from different patterns of interaction among host plants and vectors. Manipulation of vector behavior by phytovirus facilitates its propagation and seems to converge according to the virus transmission mode. However, this convergence has barely been studied in viruses infecting Brassicaceae. Methods: The present study has tested the effects of infection of the Brassicaceae plant Camelina sativa with the persistent Turnip Yellows Virus and the semi-persistent Cauliflower Mosaic Virus on (i) arrestment and dispersal, (ii) feeding behavior by electropenetrography and (iii) physiology of two aphid species: the polyphagous Myzus persicae and the Brassicaceae specialist Brevicoryne brassicae. Results/Conclusion: Results showed no evidence of evolutionary convergence in vector behavior within persistent and semi-persistent phytovirus-infected camelina. Indeed, whatever the virus species considered, infected camelina had opposite effects (i.e. negative and positive) on the feeding behavior and physiology of the two aphid species. In conclusion, viral manipulation of vector behavior could therefore depend not only on the virus mode of transmission, which is generally considered as a common assumption, but also on the aphid species. Indeed, aphid species with dissimilar dietary specialization differed in their response to the same virus infection