Aphid Behaviour Research Articles

Why aphid virus retention needs more attention: Modelling aphid behaviour and virus manipulation in non-persistent plant virus transmission.

Plant viruses threaten food security and are often transmitted by insect vectors. Non-persistently transmitted (NPT) plant viruses are transmitted almost exclusively by aphids. Because virions attach to the aphid's stylet (mouthparts) and are acquired and inoculated via brief epidermal probes, the aphid-virus interaction is highly transient, with a very short aphid virus retention time. Many NPT viruses manipulate their host plant's phenotype to change aphid behaviour to optimise virus transmission. Epidemiological models of this have overlooked a key feature of aphid NPT virus retention: probing or feeding on a plant causes aphids to lose the virus. Furthermore, experimental studies suggest aphids could possibly inoculate multiple healthy plants within one infective period if they do not feed. Consequences of this for virus manipulation of host plant phenotype have not been explored. Our new compartmental epidemiological model includes both behaviour-based aphid dispersal and infectivity loss rates, and the ability of infective aphids to probe multiple plants before virus loss. We use our model to explore how NPT virus-induced host phenotypes affect epidemic outcomes, comparing these results to representative previous models. We find that previous models behave fundamentally differently and underestimate the benefit of an 'attract-and-deter' phenotype, where the virus induces increased aphid attraction to infected plants but deters them from prolonged feeding. Our results also highlight the importance of characterising NPT virus retention upon the aphid during probing. Allowing for multiple infective probes increases disease incidence and the effectiveness of virus manipulation, with implications for epidemic prediction and control.

Impact of biopesticides on the probing and feeding behavior of Aphis gossypii

BackgroundPesticides-induced mortality has traditionally been the toxicological endpoint on which a chemical is selected for pest management strategies. However, the exposure to a pesticide might also cause behavioral alterations that can dramatically affect the dynamics of pest-plant interaction. Understanding these non-lethal effects is crucial for developing comprehensive and sustainable pest control measures.MethodsHere, using the Electrical Penetration Graph (EPG) technique, we evaluated whether biopesticides routinely used in organic or conventional pest management might alter the probing and feeding behavior of the cotton aphid Aphis gossypii on treated plants. The post exposure persistence of feeding alterations when moving the insect onto clean plants was also assessed. The tested biopesticides were chosen for being aphicides or because used in those crops hosts of A. gossypii. Generalised linear mixed models were fitted to analyse the effects of biopesticides on the probing and feeding behavior of aphids, using untreated control data as a model baseline.ResultsResiduals of Bacillus thuringiensis, Beauveria bassiana, and sulfur significantly affected the dynamics of the stylets intercellular route compared to the control (namely, shorter pathways, fewer and shorter brief intracellular stylets probes, higher and longer derailed stylets events). Mineral oil, orange essential oil and pyrethrin delayed or impaired the onset of phloem sap ingestion. On the other hand, copper and potassium salts promoted feeding. Pyrethrin was the only biopesticides inducing persistent behavioral alterations, with insects displaying a higher frequency of occurrence of xylem ingestion events when moved to untreated plants after exposure.ConclusionsOverall, this study demonstrates that biopesticides modulate the aphid-plant interactions by impairing or facilitating the exploitation of the host plant, also affecting the patterns conducive to plant pathogens transmission. This study also highlights the importance of considering in toxicological studies the impact of all the compounds the pest could be exposed to within the agroecosystem, including those not designed for that specific pest.

Why aphid virus retention needs more attention: modelling aphid behaviour and virus manipulation in non-persistent plant virus transmission.

Abstract Plant viruses threaten food security and are often transmitted by insect vectors. Non-persistently transmitted (NPT) plant viruses are transmitted almost exclusively by aphids. Because virions attach to the aphid's stylet (mouthparts) and are acquired and inoculated via brief epidermal probes, the aphid-virus interaction is highly transient, with a very short aphid virus retention time. Many NPT viruses manipulate their host plant's phenotype to change aphid behaviour to optimise virus transmission. Epidemiological models of this have overlooked a key feature of aphid NPT virus retention: probing or feeding on a plant causes aphids to lose the virus. Additionally, experimental studies suggest aphids could possibly inoculate multiple healthy plants within one infective period. However, consequences of this for virus manipulation of host plant phenotype have not been explored. Our new compartmental epidemiological model includes both behaviour-based aphid dispersal and infectivity loss rates, and the ability of infective aphids to probe more than one plant before virus loss. We use our model to explore how NPT virus-induced host phenotypes affect epidemic outcomes, comparing these results to representative previous models. We find that previous models behave fundamentally differently and underestimate the benefit of an 'attract-and-deter' phenotype, where the virus induces increased aphid attraction to infected plants but deters them from prolonged feeding. Our results also highlight the importance of characterising NPT virus retention upon the aphid during probing. Allowing for multiple infective probes increases disease incidence and the effectiveness of virus manipulation, with implications for epidemic prediction and control.

Hesperidin as a Species-Specific Modifier of Aphid Behavior.

Hesperidin is a highly bioactive natural flavonoid whose role in ecological interactions is poorly known. In particular, the effects of hesperidin on herbivores are rarely reported. Flavonoids have been considered as prospective biopesticides; therefore, the aim of the present study was to examine the influence of hesperidin on the host plant selection behavior of three aphid (Hemiptera: Aphididae) species: Acyrthosiphon pisum Harrris, Rhopalosiphum padi (L.), and Myzus persicae (Sulz.). The aphid host plants were treated with 0.1% and 0.5% ethanolic solutions of hesperidin. Aphid probing behavior in the no-choice experiment was monitored using electropenetrography and aphid settling on plants in the choice experiment was recorded. The results demonstrated that hesperidin can be applied as a pre-ingestive, ingestive, and post-ingestive deterrent against A. pisum, as an ingestive deterrent against R. padi, and as a post-ingestive deterrent against M. persicae using the relatively low 0.1% concentration. While in A. pisum the deterrent effects of hesperidin were manifested as early as during aphid probing in peripheral plant tissues, in M. persicae, the avoidance of plants was probably the consequence of consuming the hesperidin-containing phloem sap.

Effects of Climate Change on the Spread and Severity of Potato Virus Y: An In-depth Examination

Potatoes are a cornerstone of global agriculture and a fundamental component of diets worldwide, with plant viruses accounting for nearly half of the emerging crop epidemics. Among these, Potato Virus Y (PVY) poses a formidable challenge to potato farming, leading to significant economic repercussions and threats to food security. Understanding the influence of climate on PVY is pivotal in tackling this viral menace. Climatic conditions, including temperature, precipitation, and humidity, play a key role in the behavior of aphids, the primary vectors of PVY, thereby impacting the disease's prevalence in potato fields. With climate change modifying these key weather variables, there's a looming risk of enhanced PVY spread and a shift in its geographical presence. Recognizing and adapting to these climate-induced changes is vital for formulating effective strategies and sustainable practices to counter PVY's effects, safeguarding potato crops from this major viral threat. This analysis delves into the complex dynamics between climate change and PVY, focusing on how changes in weather patterns influence the virus's behavior and impact, with the aim of enhancing our preparedness and response to this agricultural challenge.

Aphid gene expression following polerovirus acquisition is host species dependent.

Upon acquisition of persistent circulative viruses such as poleroviruses, the virus particles transcytose through membrane barriers of aphids at the midgut and salivary glands via hemolymph. Such intricate interactions can influence aphid behavior and fitness and induce associated gene expression in viruliferous aphids. Differential gene expression can be evaluated by omics approaches such as transcriptomics. Previously conducted aphid transcriptome studies used only one host species as the source of virus inoculum. Viruses typically have alternate hosts. Hence, it is not clear how alternate hosts infected with the same virus isolate alter gene expression in viruliferous vectors. To address the question, this study conducted a transcriptome analysis of viruliferous aphids that acquired the virus from different host species. A polerovirus, cotton leafroll dwarf virus (CLRDV), which induced gene expression in the cotton aphid, Aphis gossypii Glover, was assessed using four alternate hosts, viz., cotton, hibiscus, okra, and prickly sida. Among a total of 2,942 differentially expressed genes (DEGs), 750, 310, 1,193, and 689 genes were identified in A. gossypii that acquired CLRDV from infected cotton, hibiscus, okra, and prickly sida, respectively, compared with non-viruliferous aphids that developed on non-infected hosts. A higher proportion of aphid genes were overexpressed than underexpressed following CLRDV acquisition from cotton, hibiscus, and prickly sida. In contrast, more aphid genes were underexpressed than overexpressed following CLRDV acquisition from okra plants. Only four common DEGs (heat shock protein, juvenile hormone acid O-methyltransferase, and two unannotated genes) were identified among viruliferous aphids from four alternate hosts. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations indicated that the acquisition of CLRDV induced DEGs in aphids associated with virus infection, signal transduction, immune systems, and fitness. However, these induced changes were not consistent across four alternate hosts. These data indicate that alternate hosts could differentially influence gene expression in aphids and presumably aphid behavior and fitness despite being infected with the same virus isolate.

Aphids May Facilitate the Spread of Sclerotinia Stem Rot in Oilseed Rape by Carrying and Depositing Ascospores.

Aphids and Sclerotinia stem rot in oilseed rape are often studied in isolation, and their relationship is rarely explored. Our field studies have revealed a significant positive correlation between the number of aphids and the incidence of Sclerotinia stem rot. Hence, starting with the colonizing stages of the two pests, Breveroryne brassicae was assessed for its potential to acquire, transmit, and inoculate Sclerotinia sclerotiorum by being sprayed with an ascospore suspension. Moreover, distinctions in aphid feeding behavior were examined between aphids on inoculated/uninoculated winter and spring oilseed rape plants or aphids, both with and without S. sclerotiorum ascospores, using electropenetrography (EPG). The results showed that aphid feeding followed by dropping ascospore suspension significantly increased the incidence of S. sclerotiorum. Ascospores were able to adhere to aphids and were carried by aphids to healthy plants, causing disease. The results of the EPG analysis indicated that aphid feeding behavior was significantly altered in all leaf tissue levels following infection with S. sclerotiorum. Specifically, aphids initiated their first puncture significantly sooner, began probing mesophyll cells earlier, had a significantly shorter pathway duration, and secreted saliva more frequently but reduced salivation prior to feeding and ingestion compared to aphids feeding on uninfected oilseed rape. Additionally, the feeding behavior of aphids carrying ascospores was markedly different from that of aphids not carrying ascospores, implying that ascospores directly influence aphid feeding behavior but that this influence appeared to be beneficial only for S. sclerotiorum infection. Aphids carrying ascospores started to puncture cells more quickly, with a significant increase in the frequency and duration of short probes and cell punctures, shortened pathway durations, and reduced salivation before feeding compared to aphids not carrying ascospores. It is clear that there is an interaction between aphids and S. sclerotiorum. The impact of S. sclerotiorum on aphid feeding behavior is directional, favoring the spread of the fungus.

Understanding the onion aphid Neotoxoptera formosana's (Hemiptera: Aphididae) interaction with Allium (Asparagales: Amaryllidaceae) crops: a comprehensive study of feeding patterns and life history traits.

The onion aphid, Neotoxoptera formosana, poses a significant threat to Allium crops worldwide, causing considerable economic losses and quality degradation. To develop effective pest management strategies, it is crucial to understand the feeding behavior and life history of this pest on different Allium crops. In this study, the electrical penetration graph (EPG) technique was used to monitor the thorn-feeding behavior of the onion aphid on 4 Allium crops: leek, chive, garlic, and shallot. The EPG data revealed distinct feeding patterns, with garlic and shallots being more preferred hosts than chives. Additionally, the aphids primarily fed on the phloem in garlic and shallots. Analysis of life history trait showed that chives provided the most favorable conditions for aphid development and reproduction, while leek exhibited relatively unfavorable conditions. Examination of leaf histology also revealed differences among the crops, which may influence aphid feeding behavior. This study provides valuable insights into the interaction between the onion aphid and different Allium crops, aiding in the development of comprehensive pest control strategies to minimize crop damage and economic losses. The use of advanced techniques like EPG contributes to a more detailed understanding of aphid behavior and shows promise for improving pest management in other plant-pest interactions.

Discovery and properties of novel analogues of the aphid pheromones nepetalactone and nepetalactol.

Pheromones have unique advantages for pest control. Current aphid pheromone research focuses on alarm and sex pheromones. However, practical applications are limited so far, as (E)-β-farnesene has only been investigated to a small extent as an alarm pheromone and only male aphids are targeted by sex pheromones. Previous literature reports electrophysiological responses and repellent behavior of asexual aphids to nepetalactone (1B), therefore our objective was to modify nepetalactone's structure to identify key fragments responsible for repellent effects, as guidance for subsequent modifications and further investigation. In this study, seven derivatives were designed and synthesized based on nepetalactol (1A) and nepetalactone (1B) as lead compounds. Free-choice tests, conducted using cowpea aphids (Aphis craccivora), revealed that the lactone moiety was crucial for the repellent activity, and the removal of the carbonyl group eliminated the repelling effect. Compound (±)1I, an analogue of nepetalactone (1B), demonstrated a significantly higher repellent value than nepetalactone (1B) at three different concentrations, and even at 0.1 mg/mL it maintained a considerable repellent effect (26.5%). Electrostatic potential and density functional theory calculations supported the importance of the carbonyl group for the repellent effects. The newly discovered para-pheromone (±)1I shows improved repellent effects and potential for development as a novel biological control agent. Based on our innovative findings, analogues with improved efficacy and properties can be designed and prepared. Our research contributes to understanding the effects of structural modifications on pheromone activity and properties, which is crucial for exploring novel pheromone-based products for crop protection. © 2024 Society of Chemical Industry.

Endosymbionts modulate virus effects on aphid-plant interactions

Vector-borne pathogens frequently modify traits of their primary hosts and vectors in ways that influence disease transmission. Such effects can themselves be altered by the presence of other microbial symbionts, yet we currently have limited understanding of these interactions. Here we show that effects of pea enation mosaic virus (PEMV) on interactions between host plants and aphid vectors are modulated by the presence of different aphid endosymbionts. In a series of laboratory assays, we found strong interactive effects of virus infection and endosymbionts on aphid metabolomic profiles, population growth, behavior, and virus transmission during aphid feeding. Furthermore, the strongest effects—and those predicted to favor virus transmission—were most apparent in aphid lines harboring particular endosymbionts. These findings show that virus effects on host-vector interactions can be strongly influenced by other microbial symbionts and suggest a potentially important role for such interactions in disease ecology and evolution.

Viruliferous and non‐viruliferous aphids behave differently to enhance the spread of the virus

AbstractPlant viruses can modulate insect vector behaviour directly and/or indirectly by altering plant biochemistry. In many instances, such behavioural alterations increase the frequency of encounters between host and vector, leading to enhanced virus dispersal in ecosystems. In the current study using Cucumber mosaic virus (CMV), Capsicum annuum L. (Solanaceae), and Myzus persicae (Sulzer) (Hemiptera: Aphididae) as a pathosystem, we evaluated the direct and indirect effects of CMV on M. persicae biology and behavioural responses. Data showed that CMV indirectly modulates the aphid vector by providing fitness benefits to aphids, leading to enhanced aphid reproduction on CMV‐infected pepper plants in comparison with non‐infected C. annuum plants. Furthermore, CMV can also alter aphid behaviour directly by modulating the behavioural response of viruliferous aphids towards non‐infected plants. We demonstrate that CMV directly and indirectly modulates the insect vector thereby enhancing its transmission in agroecosystems.

Why do viruses make aphids winged?

Aphids are hosts to diverse viruses and are important vectors of plant pathogens. The spread of viruses is heavily influenced by aphid movement and behaviour. Consequently, wing plasticity (where individuals can be winged or wingless depending on environmental conditions) is an important factor in the spread of aphid-associated viruses. We review several fascinating systems where aphid-vectored plant viruses interact with aphid wing plasticity, both indirectly by manipulating plant physiology and directly through molecular interactions with plasticity pathways. We also cover recent examples where aphid-specific viruses and endogenous viral elements within aphid genomes influence wing formation. We discuss why unrelated viruses with different transmission modes have convergently evolved to manipulate wing formation in aphids and whether this is advantageous for both host and virus. We argue that interactions with viruses are likely shaping the evolution of wing plasticity within and across aphid species, and we discuss the potential importance of these findings for aphid biocontrol.

Comparative morphology and plant volatile responses of antennal sensilla in Cinara cedri (Hemiptera: Lachninae), Eriosoma lanigerum (Hemiptera: Eriosomatinae), and Therioaphis trifolii (Hemiptera: Calaphidinae).

Olfaction is important for mediating aphid behaviors and is involved in host location and mating. Antennal primary rhinaria play a key role in the chemoreception of aphids. The function of the peripheral olfactory system in the subfamily Aphidinae has been intensively studied, but little is known about other subfamilies of Aphididae. Therefore, three aphid species were selected to study the olfactory reception of plant volatiles: Cinara cedri (Lachninae), Eriosoma lanigerum (Eriosomatinae), and Therioaphis trifolii (Calaphidinae). In this study, the morphology and distribution of the antennal sensilla of apterous adults were observed by scanning electron microscopy. Three morphological types were identified (placoid sensilla, coeloconic sensilla, and trichoid sensilla); the first two were distributed on the antennal primary rhinaria. A pattern of primary rhinaria in C. cedri was found that differed from that of E. lanigerum and T. trifolii and consists of 1 large placoid sensillum (LP) on the 4th segment, 2 LPs on the 5th segment, and a group of sensilla on the 6th antennal segments. Later, we recorded and compared neuronal responses of the distinct placoid sensilla in the primary rhinaria of the three aphid species to 18 plant volatiles using a single sensillum recording (SSR) technique. The results indicated that the functional profiles based on the tested odorants of the primary rhinaria of the three investigated aphid species were clustered into three classes, and exhibited excitatory responses to certain types of odorants, especially terpenes. In C. cedri, the ORNs in LP6 exhibited the highest responses to (±)-citronellal across all tested chemicals, and showed greater sensitivity to (±)-citronellal than to (+)-limonene. ORNs in LP5 were partially responsive to α-pinene and (-)-β-pinene in a dose-dependent manner. Across different species, E. lanigerum showed significantly stronger neuronal responses of LP5 to several terpenes, such as (-)-linalool and α-terpineol, compared to other species. In T. trifolii, the neuronal activities in LP6 showed a greater response to methyl salicylate as compared to LP5. Overall, our results preliminarily illustrate the functional divergence of ORNs in the primary rhinaria of aphids from three subfamilies of Aphididae and provide a basis for better understanding the mechanism of olfactory recognition in aphids.

Arbuscular mycorrhizal fungus changes alfalfa (Medicago sativa) metabolites in response to leaf spot (Phoma medicaginis) infection, with subsequent effects on pea aphid (Acyrthosiphon pisum) behavior.

Plant disease occurs simultaneously with insect attack. Arbuscular mycorrhizal fungi (AMF) modify plant biotic stress response. Arbuscular mycorrhizal fungi and pathogens may modify plant volatile organic compound (VOC) production and insect behavior. Nevertheless, such effects are rarely studied, particularly for mesocosms where component organisms interact with each other. Plant-mediated effects of leaf pathogen (Phoma medicaginis) infection on aphid (Acyrthosiphon pisum) infestation, and role of AMF (Rhizophagus intraradices) in modifying these interactions were elucidated in a glasshouse experiment. We evaluated alfalfa disease occurrence, photosynthesis, phytohormones, trypsin inhibitor (TI) and total phenol response to pathogen and aphid attack, with or without AMF, and aphid behavior towards VOCs from AMF inoculated and non-mycorrhizal alfalfa, with or without pathogen infection. AM fungus enhanced alfalfa resistance to pathogen and aphid infestation. Plant biomass, root : shoot ratio, net photosynthetic rate, transpiration rate, stomatal conductance, salicylic acid, and TI were significantly increased in AM-inoculated alfalfa. Arbuscular mycorrhizal fungi and pathogen significantly changed alfalfa VOCs. Aphids preferred VOCs of AM-inoculated and nonpathogen-infected to nonmycorrhizal and pathogen-infected alfalfa. We propose that AMF alter plant response to multiple biotic stresses in ways both beneficial and harmful to the plant host, providing a basis for strategies to manage pathogens and herbivore pests.

Probing behavior of Aphis fabae and Myzus persicae on three species of grapevines with analysis of grapevine leaf anatomy and allelochemicals

The peach-potato aphid Myzus persicae (Sulzer) and the black bean aphid Aphis fabae Scopoli are polyphagous and cosmopolitan hemipterans, therefore they can infest grapevines in all areas of cultivation. Electrical Penetration Graph (EPG) technique was applied to monitor the probing behavior of A. fabae and M. persicae on Vitis amurensis Rupr., Vitis riparia Michaux, and Vitis vinifera L. The content of major flavonoids and stilbenoids in grapevine leaves and epidermal thickness, distance between abaxial leaf surface and phloem, and the simulated shortest pathway from epidermis to phloem that might have affected aphid probing were also analyzed. Aphid probing was limited mainly to non-vascular tissues on the three studied grapevine species. Phloem phase occurred in 32%, 14%, and 6% of A. fabae and in 76%, 39%, and 74% of M. persicae on V. amurensis, V. riparia and V. vinifera, respectively. Phloem phase consisted of only salivation into sieve elements and lasted less than 2.5 minutes on average in all aphids. The time to reach the first phloem phase on grapevines was 5.0 hours in A. fabae and 2.6–3.6 hours in M. persicae. Of the analyzed flavonoids, catechin, epicatechin, and quercetin occurred in all grapevine species, while rutin – in V. amurensis and V. riparia and isorhamnetin only in V. amurensis. Of the analyzed stilbenoids, piceid occurred in all grapevines, resveratrol in V. amurensis and V. vinifera, and ε-viniferin only in V. vinifera. Aphid behavior demonstrated that V. amurensis, V. riparia and V. vinifera are not attractive host plants to A. fabae and M. persicae. It is likely that the content of flavonoids and stilbenoids contributes to the limited susceptibility of the three grapevine species to A. fabae and M. persicae, while the observed slight differences in the anatomical structure of the leaves seem not significant in this context.

Volatile interactions between specific undamaged barley cultivars affect aphid feeding behavior and performance

Recent studies have demonstrated that cultivar mixtures can reduce aphid plant acceptance and population development. It is still unknown as to which underlying mechanisms may contribute to this phenomenon. We investigated the effects of volatile interactions between undamaged barley cultivars on aphid feeding behavior and performance in the laboratory. Spring barley (Hordeum vulgare L.) cultivar Salome was exposed to volatiles from Fairytale (SeF), Anakin (SeA), or clean air (Se0). We used an electrical penetration graph to test the effect of exposure to neighbor volatiles on the feeding behavior and performance of bird cherry-oat aphids (Rhopalosiphum padi L.). We also assessed aphid relative growth rate, intrinsic rate of increase, and development time on exposed and unexposed Salome plants. Aphids spent significantly longer time on epidermis and mesophyll plant tissues on SeF than Se0, and no difference was observed between SeA and Se0. Significant decreases in the duration of phloem ingestion and phloem sustained ingestion were recorded in SeF showing that volatile-induced effects cause difficulty for aphids to feed. However, no differences in these variables were detected between SeA and Se0. We also observed reduced aphid relative growth rate and intrinsic rate of increase on SeF compared to Se0 and SeA. Our study demonstrated that, in a specific combination, exposure of one barley cultivar to volatiles from another one can change aphid feeding behavior and performance, probably due to changes in host plant properties/quality. Our results provide an insightful explanation of mechanisms responsible for the reduced aphid population development previously observed in the field.

The phloem lectin PP2-A1 enhances aphid resistance by affecting aphid behavior and maintaining ROS homeostasis in cucumber plants

Aphid (Aphis gossypii Glover) attack frequently results in a significant loss of output and deterioration of fruit quality in cucumber (Cucumis sativus L.). Phloem protein 2 (PP2) is conserved as a phloem lectin in plants, and few studies have been conducted on the regulatory mechanism of PP2. Based on our previous study of CsPP2-A1 in cucumber, to further investigate the biological function of CsPP2-A1, we compared the changes of selectivity, non-selectivity, colonization, reproductions of aphids, and the phenotype in wild type (WT), CsPP2-A1 overexpressing (CsPP2-A1-OE), and CsPP2-A1 interfering (CsPP2-A1-RNAi) cucumber plants after inoculation with aphids. We found that CsPP2-A1-OE cucumber plants generated resistance to aphids. The aphid colonization rate and number of reproductions of CsPP2-A1-OE cucumber plants were significantly lower than that of WT and CsPP2-A1-RNAi cucumber plants. Through Pearson's correlation and principal component analysis (PCA), it was found that CsPP2-A1 played a crucial role in the balance of reactive oxygen species (ROS) in plants. Overexpression of the CsPP2-A1 resulted in increased levels of antioxidant enzyme, eliminating ROS and preventing the damage by ROS in cucumber. Furthermore, nutritional imbalance for aphids and content of secondary metabolites were increased in overexpressed CsPP2-A1 cucumber plants, and thus preventing aphid attack. These together may improve cucumber resistance against aphids and the mechanism of CsPP2-A1 defense against aphids was preliminarily explored.

Sorghum cuticular waxes influence host plant selection by aphids.

Quantification of cuticular waxes coupled with insect bioassays and feeding behavior analysis demonstrate that long-chain C32 fatty alcohol impacts host plant selection by aphids. Cuticular waxes constitute the first point of contact between plants and their environment, and it also protect plants from external stresses. However, the role of waxes in Sorghum bicolor (sorghum) against sugarcane aphid (Melanaphis sacchari), a relatively new and devastating pest of sorghum in the U.S., is not fully understood. In this study, we monitored sugarcane aphid behavior on two genotypes of young sorghum plants with different wax chemistry: a wild-type plant (bloom) with lower C32 alcohol cuticular wax, and a mutant plant (bloomless) with 1.6 times the amount of wax compared to wild-type plants. No-choice aphid bioassays revealed that sugarcane aphid reproduction did not vary between wild-type and the bloomless plants. Electrical Penetration Graph (EPG) monitoring indicated that the sugarcane aphids spent comparable amount of time feeding from the sieve elements of the wild-type and bloomless plants. However, aphids spent more time feeding on the xylem sap of the bloomless plants compared to the wild-type plants. Furthermore, aphid choice assays revealed that the sugarcane aphids preferred to settle on bloomless compared to wild-type plants. Overall, our results suggest that cuticular waxes on young sorghum leaves play a critical role in influencing host plant selection by sugarcane aphids.

Turnip Mosaic Virus Infection Differentially Modifies Cabbage Aphid Probing Behavior in Spring and Winter Oilseed Rape (Brassica napus).

Simple SummaryWinter oilseed rape accounts for about 90% of total oilseed rape planting area in China, with the majority of it concentrated in the Yangtze River basin. The remaining 10% is mostly found in the provinces of China’s northwest plateau. Winter oilseed rape areas in China have gradually expanded to the north in the last decade, resulting in cabbage aphids and turnip mosaic virus (TuMV). The aphid is a vector for TuMV and is gradually increasing on winter and spring oilseed rape. Quantifying the probing behaviors of the aphids on spring oilseed rape and winter oilseed rape helps us to understand TuMV regulation of the aphids. We found that compared to mock-inoculated plants, cabbage aphids on infected plants increased brief probing frequency, cell penetration frequency, intracellular probing time, decreased time to first probe and pathway duration, potentially promoting viral acquisition and minimizing viral loss and plant damage. Viruliferous aphids had reduced pathway duration, increased cell penetration frequency, increased intracellular probing time, increased salivation frequency, and ingested less sap compared with non-viruliferous aphids, primed for viral infection. TuMV infection also differentially modified aphid feeding behavior on winter and spring oilseed rape cultivars, primarily on uninfected plants.Direct and indirect effects of plant virus infection on vector behavior have been discovered to improve virus transmission efficiency, but the impact of plant cultivars in virus–vector–plant interactions has received little attention. Electropenetrography (EPG) allows real-time tracking and quantification of stylet penetration behaviors, pathogen transmission, and plant resistance mechanisms. Quantitative probing behaviors on a spring oilseed rape cultivar, ‘Xinyou17’, and a winter oilseed rape cultivar, ‘Zheping4’, were investigated using EPG to compare turnip mosaic virus (TuMV) regulation of cabbage aphid probing behavior. Results for indirect effects showed that compared to mock-inoculated plants, cabbage aphids on infected plants increased brief probing frequency, cell penetration frequency, intracellular probing time, and decreased time to first probe and pathway time, potentially promoting viral acquisition. TuMV also directly influences aphid probing behavior. Viruliferous aphids had reduced pathway time, increased cell penetration frequency, increased intracellular probing time, increased salivation frequency, and ingested less sap than non-viruliferous aphids, primed for viral infection. Although oilseed rape cultivars can also influence aphid behavior, the main effect of cultivars was not significant on TuMV-infected plants.

A conserved odorant receptor identified from antennal transcriptome of Megoura crassicauda that specifically responds to cis-jasmone

Herbivore-induced plant volatiles (HIPVs) play a key role in the interactions between plants and herbivorous insects, as HIPVs can promote or deter herbivorous insects’ behavior. While aphids are common and serious phloem-feeding pests in farmland ecosystems, little is known about how aphids use their sensitive olfactory system to detect HIPVs. In this study, the antennal transcriptomes of the aphid species Megoura crassicauda were sequenced, and expression level analyses of M. crassicauda odorant receptors (ORs) were carried out. To investigate the chemoreception mechanisms that M. crassicauda uses to detect HIPVs, we performed in vitro functional studies of the ORs using 11 HIPVs reported to be released by aphid-infested plants. In total, 54 candidate chemosensory genes were identified, among which 20 genes were ORs. McraOR20 and McraOR43 were selected for further functional characterization because their homologs in aphids were quite conserved and their expression levels in antennae of M. crassicauda were relatively high. The results showed that McraOR20 specifically detected cis-jasmone, as did its ortholog ApisOR20 from the pea aphid Acyrthosiphon pisum, while McraOR43 did not respond to any of the HIPV chemicals that were tested. This study characterized the ability of the homologous OR20 receptors in the two aphid species to detect HIPV cis-jasmone, and provides a candidate olfactory target for mediating aphid behaviors.