Aphid Vectors Research Articles

Population dynamics of Melanaphis sacchari (Zehntner), the aphid vector of sugarcane yellow leaf virus under tropical conditions in India

Population dynamics of Melanaphis sacchari (Zehntner), the aphid vector of sugarcane yellow leaf virus under tropical conditions in India

Characterization and Mapping of retr04, retr05 and retr06 Broad-Spectrum Resistances to Turnip Mosaic Virus in Brassica juncea, and the Development of Robust Methods for Utilizing Recalcitrant Genotyping Data.

Turnip mosaic virus (TuMV) induces disease in susceptible hosts, notably impacting cultivation of important crop species of the Brassica genus. Few effective plant viral disease management strategies exist with the majority of current approaches aiming to mitigate the virus indirectly through control of aphid vector species. Multiple sources of genetic resistance to TuMV have been identified previously, although the majority are strain-specific and have not been exploited commercially. Here, two Brassica juncea lines (TWBJ14 and TWBJ20) with resistance against important TuMV isolates (UK 1, vVIR24, CDN 1, and GBR 6) representing the most prevalent pathotypes of TuMV (1, 3, 4, and 4, respectively) and known to overcome other sources of resistance, have been identified and characterized. Genetic inheritance of both resistances was determined to be based on a recessive two-gene model. Using both single nucleotide polymorphism (SNP) array and genotyping by sequencing (GBS) methods, quantitative trait loci (QTL) analyses were performed using first backcross (BC1) genetic mapping populations segregating for TuMV resistance. Pairs of statistically significant TuMV resistance-associated QTLs with additive interactive effects were identified on chromosomes A03 and A06 for both TWBJ14 and TWBJ20 material. Complementation testing between these B. juncea lines indicated that one resistance-linked locus was shared. Following established resistance gene nomenclature for recessive TuMV resistance genes, these new resistance-associated loci have been termed retr04 (chromosome A06, TWBJ14, and TWBJ20), retr05 (A03, TWBJ14), and retr06 (A03, TWBJ20). Genotyping by sequencing data investigated in parallel to robust SNP array data was highly suboptimal, with informative data not established for key BC1 parental samples. This necessitated careful consideration and the development of new methods for processing compromised data. Using reductive screening of potential markers according to allelic variation and the recombination observed across BC1 samples genotyped, compromised GBS data was rendered functional with near-equivalent QTL outputs to the SNP array data. The reductive screening strategy employed here offers an alternative to methods relying upon imputation or artificial correction of genotypic data and may prove effective for similar biparental QTL mapping studies.

Quantitative Trait Locus Mapping of Resistance to Turnip Yellows Virus in Brassica rapa and Brassica oleracea and Introgression of These Resistances by Resynthesis Into Allotetraploid Plants for Deployment in Brassica napus.

Turnip yellows virus (TuYV) is aphid-transmitted and causes considerable yield losses in oilseed rape (OSR, Brassica napus, genome: AACC) and vegetable brassicas. Insecticide control of the aphid vector is limited due to insecticide resistance and the banning of the most effective active ingredients in the EU. There is only one source of TuYV resistance in current commercial OSR varieties, which has been mapped to a single dominant quantitative trait locus (QTL) on chromosome A04. We report the identification, characterisation, and mapping of TuYV resistance in the diploid progenitor species of OSR, Brassica rapa (genome: AA), and Brassica oleracea (genome: CC). Phenotyping of F1 populations, produced from within-species crosses between resistant and susceptible individuals, revealed the resistances were quantitative and partially dominant. QTL mapping of segregating backcross populations showed that the B. rapa resistance was controlled by at least two additive QTLs, one on chromosome A02 and the other on chromosome A06. Together, they explained 40.3% of the phenotypic variation. In B. oleracea, a single QTL on chromosome C05 explained 22.1% of the phenotypic variation. The TuYV resistance QTLs detected in this study are different from those in the extant commercial resistant varieties. To exploit these resistances, an allotetraploid (genome: AACC) plant line was resynthesised from the interspecific cross between the TuYV-resistant B. rapa and B. oleracea lines. Flow cytometry confirmed that plantlets regenerated from the interspecific cross had both A and C genomes and were mixoploid. To stabilise ploidy, a fertile plantlet was self-pollinated to produce seed that had the desired resynthesised, allotetraploid genome AACC. Phenotyping of the resynthesised plants confirmed their resistance to TuYV. Genotyping with resistance-linked markers identified during the mapping in the progenitors confirmed the presence of all TuYV resistance QTLs from B. rapa and B. oleracea. This is the first report of TuYV resistance mapped in the Brassica C genome and of an allotetraploid AACC line possessing dual resistance to TuYV originating from both of its progenitors. The introgression into OSR can now be accelerated, utilising marker-assisted selection, and this may reduce selection pressure for TuYV isolates that are able to overcome existing sources of resistance to TuYV.

Potential Aphid (Hemiptera: Aphididae) Vectors of Plum-pox Virus (Virus:Potyviridae) and Status of Sharka Disease in Stone Fruit Orchards in the East Mediterranean Region of Turkey

This study was conducted in stone fruit orchards in five provinces of the East Mediterranean Region of Turkey between the years of 2009-2011. The aim of the study was to determine the potential aphid vectors of the quarantine pathogen PPV (plum pox virus, family Potyviridae) that causes serious yield losses. During the surveys, 542 orchard/nurseries were sampled and 6 aphid species (Hemiptera: Aphididae) [Brachycaudus persicae (Passerini,1860), B. helichrysi (Kaltenbach, 1843), B. cardui (Linnaeus, 1758), Hyalopterus pruni (Geoffroy, 1762), Myzus persicae (Sulzer, 1776) and M.cerasi (Fabricius, 1775)] from stone fruit trees and 4 aphid species [Aphis craccivora (Koch, 1854), A. fabae Scopoli 1763, A. gossypii Glover 1877, A. nasturtii Kaltenbach 1843)] from weeds that were known as the efficient vectors of PPV were detected in the stone fruit orchards. Stone fruit samples (flower, leaf, fruit), weed samples and aphid samples were tested by DAS-ELISA to determine the presence of PPV. PPV infected samples that resulted uncertain from DAS-ELISA were processed to conventional RT-PCR (Reverse Transcription Polymerase Chain Reaction) to finalize the decision of PPV presence. A total of 8 orchards were resulted as PPV-infected with both analyzing methods in the region. Three of these orchards were infected with aphids as well. B.cardui collected from the PPV-infected orchard in Hatay-Samandağ were also run to analyse for the presence of PPV and resulted virus positive.

Rescue of an Infectious cDNA Clone of Barley Yellow Dwarf Virus-GAV.

Barley yellow dwarf virus-GAV (BYDV-GAV) is one of the most prevalent viruses causing yellow dwarf disease in wheat in China. The biology and pathology of BYDV-GAV are well studied; however, gene functions and molecular mechanisms of BYDV-GAV disease development are unclear because of the lack of a reverse genetics system. In this study, a full-length complementary DNA (cDNA) clone of BYDV-GAV was constructed and expressed via Agrobacterium-mediated inoculation of Nicotiana benthamiana. Virions produced by BYDV-GAV in N. benthamiana were transmitted to wheat by an aphid vector after acquisition via a sandwich feeding method. Infectivity of the cDNA clone in wheat was verified via reverse transcription PCR and western blot assays, and the recombinant virus elicited typical reddening symptoms in oats and was transmitted between wheat plants. These results confirm the production of biologically active transmissible virions. Using the BYDV-GAV infectious clone, we demonstrate that viral protein P4 was involved in cell-to-cell movement and stunting symptoms in wheat. This is the first report describing the development of an infectious full-length cDNA clone of BYDV-GAV and provides a useful tool for virus-host-vector interaction studies.

Barley yellow dwarf virus-infected wheat plant modulated selection behavior of vector aphids

Barley yellow dwarf virus-infected wheat plant modulated selection behavior of vector aphids

PP 1/324 (1) Aphids, including aphid vectors of viruses, in winter oilseed rape

Specific scopeThis Standard describes the conduct of trials for the efficacy evaluation of insecticides against aphids in oilseed rape, and their effect on virus transmission.Specific approval and amendmentApproved in 2021‐09.

Silver nanoparticles as a viricidal agent to inhibit plant-infecting viruses and disrupt their acquisition and transmission by their aphid vector.

Silver nanoparticles (AgNPs) are a potentially effective tool for preventing viral plant diseases. This study was carried out to evaluate the effectiveness of AgNPs for managing bean yellow mosaic virus (BYMV) disease in faba bean plants from the plant-virus-vector interaction side. AgNPs were evaluated as foliar protective and curative agents. In addition, the effect of AgNPs on virus acquisition and transmission by its vector aphid was investigated. The results indicated that AgNPs exhibited curative viricidal activity and were able to inactivate BYMV when applied 48 hours after virus inoculation. The occurrence of disease was prevented using an AgNP concentration as low as 100 mg L-1, whereas virus infection was completely inhibited when plants were preventatively treated with AgNPs at a concentration of to 200 mg L-1 24 h before virus inoculation. AgNPs proved to be highly bio-reactive, binding to viral particles and suppressing their replication and accumulation within plant tissues. Moreover, AgNPs, at all concentrations tested, were found to upregulate the pathogenesis-related gene PR-1 and induce the production of defense-related oxidizing enzymes in treated plants. Exposure of aphids to AgNPs-treated plants before virus acquisition reduced BYMV acquisition and transmission efficiency by 40.65 to 100% at 24 h post-application, depending on the AgNP dosage. At 10 days after treatment, virus acquisition was reduced by 36.82% and 79.64% upon exposure to AgNPs at a concentration of 250 and 300 mg L-1, respectively. These results suggest that AgNPs have curative viricidal activity due to targeting the virus coat protein and affecting virus-vector interactions. Accordingly, AgNPs may contribute to alleviating the natural disease and virus transmission under field conditions. This is the first report on the activity of nanomaterials against plant virus acquisition and transmission by insects.

Evaluation of the emergency authorisations granted by Member State France for plant protection products containing imidacloprid or thiamethoxam

The European Food Safety Authority (EFSA) was requested by the European Commission to provide technical assistance in accordance with Article 53(2) of Regulation (EC) No 1107/2009 to examine the emergency authorisations granted in 2021 by the competent national authority in France for plant protection products containing the neonicotinoid active substances (a.s.) clothianidin, imidacloprid or thiamethoxam for uses on sugar beet which were restricted when all outdoor uses were prohibited in May 2018. EFSA was asked to assess whether the granting of this emergency authorisation and its wide scope was necessary because of danger which cannot be contained by any other reasonable means. In this context, EFSA collected and evaluated the information in relation to the emergency authorisation for imidacloprid and thiamethoxam in France in line with the EFSA insecticide protocol developed in the framework of a mandate concerning the application of Article 4(7) of Regulation (EC) No 1107/2009. The current technical report summarises the outcome of the evaluation of four crop/pest combinations considered in France in 2021.The evaluation demonstrated that for the examined pests (Aphis fabae, Aulacorthum solani, Macrosiphum euphorbiae, Myzus ascalonicus and Myzus persicae) vectors of the quarantine virus BYV (beet yellows virus) no alternative active substance to neonicotinoids is currently authorised in France on sugar beet for seed treatment. Foliar spraying applications against the aphid vectors of BYV can’t be considered as sufficient alternative method to the seed treatment, because they can't control the early proliferation of aphids. The evaluation included an assessment of non-insecticide alternatives for the presented uses. Seven non-chemical methods are available, but they are only moderately effective. For this reason, EFSA concluded when considering the methodology of the EFSA Article 4(7) insecticide protocol, that the emergency authorisations were scientifically supported.

Evaluation of Bean Common Mosaic Disease and Associated Aphid Vector, Aphis fabae L., on Common Bean (Phaseolus vulgaris L.) Production in Lower Eastern Kenya

Production of common bean in Kenya is constrained by pests and diseases and to improve bean yields amongst majority small-scale farmers, appropriate management strategies should be adopted. Bean common mosaic disease (BCMD) caused by bean common mosaic virus and vectored by bean aphids and infected seeds, substantially inhibit common bean production in Kenya. An extensive and diagnostic field survey was conducted in six agro ecological zones (AEZs) of lower eastern Kenya during the long and short rains of 2018 to determine BCMD incidence (BCMD-I), severity (BCMD-S), bean aphid abundance (BAA), bean aphid incidence (BAI) and the management strategies applied by farmers. Significant (P≤0.001) variations observed for these traits between bean varieties, rainy seasons and AEZs implied that farmers could select and grow a tolerant bean variety or grow a variety either in a season or an AEZ with low BCMD and bean aphid pressure. Such included AEZ-UMSA with least mean BCMD-I (42%), BCMD-S (1.9) and BAI (11%) compared to two AEZs (LHSH & LM4) that showed BCMD-I of >70%, BCMD-S >3.0 and BAI >50%. The AEZs differences could be attributed to variations in altitudes, temperature and humidity that influences vector (aphid) movement. Of the nine bean varieties identified during the survey, Selian 14 was the most preferred by farmers (at ~35%) with relatively lower BCMD-I (~49%) and BAI (~35%) compared to the least (<5%) farmer-preferred variety Wairimu that showed higher BCMD-I (56%) and BAI (~68%). Therefore variety Selian 14 was considered tolerant to BCMD and bean aphid. Significant (P≤0.001) and positive correlations (r = 0.67) between BAI and BCMD-I implied an effective control of bean aphids could reduce the impact of BCMD on bean production. On visual diagnostics, >75% of farmers could generally identify diseased or pest-infested bean crops and stage of growth of the crop most affected. None (0%) could however identify BCMD symptoms although ~40% identified the vector bean aphids with ~26% implementing some form of aphid or pest management strategy. On management, season-driven early planting and bean intercropping were the most applied strategies (>80%), crop rotation and weed control accounted for ~71%, certified seeds at 1% and non-chemical or pesticide applications (0%). Both low adoption of certified seeds and no chemical aphid control were attributed to high costs, despite the possibility the two factors could have contributed to higher incidences and severity of BCMD in the study area as the disease is both seed and vector-borne. In summary, lack of knowledge and training among farmers on diagnosis and management of aphid-pests and BCMD, were cited as the main constraints for low bean cultivation. This study therefore recommends provision of adequate extension services and farmer training in lower eastern Kenya for improved bean yield and subsequent better family livelihoods and income.

In-Field Evaluation of Drone-Released Lacewings for Aphid Control in California Organic Lettuce.

Aphids are one of the most economically important pests to California's Central Coast lettuce industry. Aphids vector the lettuce mosaic virus and are crop contaminants in the packaging of the product. Lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), is one of the predominant aphid species in lettuce, and it poses unique management challenges forming colonies inside the lettuce head. Current management practices rely on repeated foliar insecticide applications to reduce aphid densities per plant. Some organic growers have explored the release of laboratory-reared beneficial insects to manage aphids in their commercial fields. This project sought to document the effects of drone-released lacewing eggs on lettuce aphid densities in organic romaine lettuce fields. Commercially reared lacewing eggs were released at a rate of 74,131 eggs/ha and organic-certified insecticides were sprayed following their respective label recommendations. Our results could be interpreted as preliminary evidence that drone release of lacewings could reduce aphid densities (15.6-150.0 aphids/lettuce head) when compared to the untreated plots (32.1-257.9 aphids/lettuce head). Aphid densities were also decreased after the application of foliar organic-certified insecticides (11.77-143.5). Traditionally, the cost of labor has limited the use of beneficials in the lettuce production system, but the use of drones for these releases may make this strategy more attractive. Based on our calculations, spraying an organic-certified insecticide is less expensive (direct operational costs of U.S. $ 116.36/ha) than releasing beneficial insects by hand ($ 185.40) or by drone ($ 176.00) when mimicking the conditions of this study.

Vector-borne plant pathogens modify top-down and bottom-up effects on insect herbivores.

Ecological theory predicts that host-plant traits affect herbivore population growth rates, which in turn modulates predator-prey interactions. However, while vector-borne plant pathogens often alter traits of both host plants and vectors, a few studies have assessed how pathogens may act as interaction modifiers within tri-trophic food webs. By applying a food web motif framework, we assessed how a vector-borne plant pathogen (Pea-enation mosaic virus, PEMV) modified both bottom-up (plant-herbivore) and top-down (predator-prey) interactions. Specifically, we assessed trophic interactions with PEMV-infectious Acyrthosiphon pisum (pea aphid) vectors compared to non-infectious aphids in a factorial experiment that manipulated predator and plant communities. We show that PEMV altered bi-trophic relationships, whereby on certain plant species, PEMV reduced vector performance but also increased their susceptibility to predators. However, on other plant species, PEMV weakened top-down control or increased vector performance. Our results suggest that vector-borne plant pathogens are important interaction modifiers for plant-herbivore-predator dynamics: host-plant response to viruses can decrease herbivore abundance by reducing herbivore performance, but also increase herbivore abundance by weakening top-down control. Broadly speaking, trophic interactions that regulate herbivore outbreaks appear to be modified for herbivores actively transmitting viruses to host plants. Consequently, management and monitoring of outbreaking herbivores should consider the infection status of focal populations.

Responses to predation risk cues and alarm pheromones affect plant virus transmission by an aphid vector.

Herbivores assess predation risk in their environment by identifying visual, chemical, and tactile predator cues. Detection of predator cues can induce risk-avoidance behaviors in herbivores that affect feeding, dispersal, and host selection in ways that minimize mortality and reproductive costs. For herbivores that transmit plant pathogens, including many aphids, changes in herbivore behavior in response to predator cues may also affect pathogen spread. However, few studies have assessed how aphid behavioral responses to different types of predator cues affect pathogen transmission. Here, we conducted greenhouse experiments to assess whether responses of pea aphids (Acyrthosiphon pisum) to predation risk and alarm pheromone (E-β-Farnesene), an aphid alarm signal released in response to predation risk, affected transmission of Pea enation mosaic virus (PEMV). We exposed A. pisum individuals to risk cues, and quantified viral titer in aphids and pea (Pisum sativum) host plants across several time periods. We also assessed how A. pisum responses to risk cues affected aphid nutrition, reproduction, and host selection. We show that exposure to predator cues and alarm pheromone significantly reduced PEMV acquisition and inoculation. Although vectors avoided hosts with predator cues, predator cues did not alter vector reproduction or reduce nutrient acquisition. Overall, these results suggest that non-consumptive effects of predators may indirectly decrease the spread of plant pathogens by altering vector behavior in ways that reduce vector competence and pathogen transmission efficiency.

Áfidos vectores del virus del enanismo amarillo de la cebada (BYDV) en cultivo de trigo en el Paraguay

El Barley yellow dwarf virus o Virus del Enanismo Amarillo de la Cebada (BYDV) es una de las enfermedades transmitidas por áfidos presente en muchas regiones productoras de trigo del mundo, causando mermas importantes en la producción. Identificar las especies que transmiten la enfermedad es de suma importancia, a fin de encarar tácticas de manejo, para evitar la diseminación de la misma. El estudio tiene como objetivo identificar especies de áfidos transmisores del BYDV en cultivos de trigo de las zonas de mayor producción del Paraguay. Los trabajos de trampeo de especímenes se realizaron desde el inicio de la emergencia de las plántulas hasta la etapa final del cultivo de trigo que comprendió entre los meses de mayo hasta octubre del año 2014. Los insectos fueron capturados semanalmente en cada una de las parcelas seleccionadas en trampas tipo Moericke. Los datos fueron sometidos a análisis faunísticos. Se identificaron cinco especies de áfidos, Rhopalosiphum padi, Rhopalosiphum maidis, Sitobion avenae, Schizaphis graminum, Rhopalosiphum rufiabdominalis, todas las especies identificadas son consideradas transmisoras de virus.

First report of Turnip yellows virus in cabbage in the Philippines

In March 2017, 52 dried-leaf samples of brassicaceous plants from the Philippine Highlands, one of which was a sample of cabbage (Brassica oleracea var. capitata; Fig. 1), were submitted to Fera Science Ltd., via the Centre for Agriculture and Bioscience International (CABI). The plants were all displaying virus-like, yellowing symptoms (Reeder et al., 2017). Initially, samples were bulked together and tested by ELISA for the presence of viruses known to occur in the Brassicaceae including Cucumber mosaic virus (CMV) (Agdia, USA), Turnip mosaic virus (TuMV) and Turnip yellows virus (TuYV) (Loewe, Germany). All the bulked samples gave negative results for CMV, TuMV and TuYV, and the samples were also tested individually for the presence of Turnip yellow mosaic virus (TYMV) (DSMZ, Germany). All Chinese cabbage (Brassica rapa subsp. pekinensis) samples were positive for TYMV as described by Reeder et al. (2017). However, the Brassica oleracea var. capitata sample tested negative for TYMV and was therefore screened for virus infection using an Illumina MiSeq as described by Adams et al. (2014). A total of 857,018 reads were obtained from the sample, 924 were assembled to yield the complete coding sequence of a polerovirus (GenBank Accession No. MW537050). The average sequencing depth of this contig was 31. Comparison at the whole genome level initially suggested that the isolate was either Brassica yellows virus or TuYV with significant nucleotide identity (>94%) to examples of both viruses. Recombination analysis using RDP 4 (Martin et al., 2015) for both TuYV (NC003743) and BrYV (NC016038) type isolates suggested that this isolate has a small recombination event in the P3-P5 region. Filardo et al. (2021) have proposed that TuYV and BrYV are the same species and describe isolates with a similar P3-P5 recombination as within a clade (group 2) of their unified TuYV species. Therefore, this isolate has been identified as containing a group 2 TuYV. A specific real-time RT-PCR primer/probe set was designed based on both TuYV and BrYV sequences. The primer/probe sequences are as follows TuYV-F2: 5′-GCCGCYTGTTTCTCAGTTCTG-3′; TuYV-R2: 5′-RACTAACCACGAGTAAAGAAGCTCAA-3′; TuYV-P2 (probe): [FAM] 5′-ACGAGTTGCGGCAYGATCCAGC[BHQ1] -3′. Testing the Brassica oleracea var. capitata sample by the real-time RT-PCR assay yielded a positive result, whereas the sample had tested negative by ELISA, suggesting the ELISA does not detect all strains of TuYV. TuYV is widespread in cruciferous plants across mainland China, South Korea and Japan (Zhang et al., 2016) but this is the first report of TuYV in the Philippines. Further work is needed to determine the prevalence of TuYV in cruciferous plants in the Philippines and identify the key aphid vectors. This information could then be used to inform future management strategies. This testing was partially funded through the Defra-Fera Long Term Service Agreement. The authors would like to thank CABI for their support.

Influence of potato variety and PVY infection on aphid behaviour: preferences from Myzus persicae and Macrosiphum euphorbiae

In order to determine the potential effects of potato plant infected by Potato virus Y (PVY) on the biology of aphid vectors, plastic box experiments were set up to study the preference of two of the most efficient PVY vectors, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas). Aphid-plant selections were assessed 4h and 8h after aphid set in observation chamber presenting dual choices using two potato varieties, cv. Désiré e and cv. Bintje. Experiments show that both M. persicae and M. euphorbia preferentially settled on cv. Bimtie potato plants infested by PVY when compared to healthy potato plants after 4h and 8h. Compared healthy cv. Désirée plant and infested cv. Désirée plant, M. persicae tended to choose healthy plant, no significant preference for M. euphorbiae was found. When both cv. Bintje and cv. Désirée plant were infested by PVY, M. persicae tended to choose cv. Désirée plant, whereas M. euphorbiae made a choice to cv. Bintje plant. While the healthy plants were also compared, no significant preference for M. euphorbiae was observed, M. persicae preferred to cv. Désirée plant in dual-choice experiment. Results of our studies could help to further increase the knowledge on aphid dynamics and viral epidemiology in the potato cropping systems.

Cauliflower mosaic virus protein P6-TAV plays a major role in alteration of aphid vector feeding behaviour but not performance on infected Arabidopsis.

Emerging evidence suggests that viral infection modifies host plant traits that in turn alter behaviour and performance of vectors colonizing the plants in a way conducive for transmission of both nonpersistent and persistent viruses. Similar evidence for semipersistent viruses like cauliflower mosaic virus (CaMV) is scarce. Here we compared the effects of Arabidopsis infection with mild (CM) and severe (JI) CaMV isolates on the feeding behaviour (recorded by the electrical penetration graph technique) and fecundity of the aphid vector Myzus persicae. Compared to mock‐inoculated plants, feeding behaviour was altered similarly on CM‐ and JI‐infected plants, but only aphids on JI‐infected plants had reduced fecundity. To evaluate the role of the multifunctional CaMV protein P6‐TAV, aphid feeding behaviour and fecundity were tested on transgenic Arabidopsis plants expressing wild‐type (wt) and mutant versions of P6‐TAV. In contrast to viral infection, aphid fecundity was unchanged on all transgenic lines, suggesting that other viral factors compromise fecundity. Aphid feeding behaviour was modified on wt P6‐CM‐, but not on wt P6‐JI‐expressing plants. Analysis of plants expressing P6 mutants identified N‐terminal P6 domains contributing to modification of feeding behaviour. Taken together, we show that CaMV infection can modify both aphid fecundity and feeding behaviour and that P6 is only involved in the latter.

Field specific monitoring of cereal yellow dwarf virus aphid vectors and factors influencing their immigration within fields.

Neonicotinoid insecticide seed treatments were withdrawn from use on cereal crops in the European Union (EU) in 2018 exposing the crops to yellow dwarf viruses transmitted by cereal aphids. To reduce prophylactic pyrethroid sprays there is a need for easier, field-specific monitoring techniques given that pest incidence is spatially and temporally highly sporadic. A field-specific monitoring method based on the use of yellow sticky traps mounted horizontally just above the crop was developed and evaluated to determine: (i) predictive capabilities of the sticky trap system, (ii) practicalities of use by farmers and agronomists, and (iii) whether landscape composition, boundary type and type of tillage affect immigration of aphid vectors. Yellow sticky traps effectively sampled winged cereal aphids and identified spatial differences in immigration patterns within- and between fields. Farmers and agronomist's aphid identification skills need improving, although they could detect aphid trends with minimal training. At least three times more cereal aphids were captured in crop headlands, especially next to taller field boundaries indicating that wind currents determined aphid immigration patterns within fields. Considerable between field aphid immigration was detected (24% of fields had no aphid immigration) even on the same farm. Levels of immigrating grain aphids were positively related to the proportion of grassland in the landscape. Tillage type had no impact on levels of immigrating aphids. Field-based monitoring and different management of headland areas could be used to reduce insecticide usage when controlling of cereal/barley yellow dwarf virus.

Modeling potato virus Y disease dynamics in a mixed-cropping system

ABSTRACT Potato virus Y (PVY) is a serious pathogen that causes yield reduction and seed degeneration in potatoes crops. It is transmitted non-persistently by a wide range of aphid vectors. The transmission process is rapid and can be affected by vector behavior exhibited during host search and feeding. Controlling aphids by insecticide is inefficient to manage PVY while, mixed-cropping system comprises potatoes and non-host crop plants is an important strategy. Studies about the significance of such practices will benefit smallholder farmers. We formulate a mathematical model that aims to investigate effects of mixed-cropping system on the PVY disease dynamics. Analysis results show that the non-virus host plant is important to reduce the basic reproduction number, of the disease. If , then the disease-free equilibrium is globally stable; if , then an endemic equilibrium exists which is locally asymptotically stable. We employed a geometric approach and discuss conditions for global stability of the endemic equilibrium. Bifurcation and sensitivity analysis of the embedded parameters were also carried out. Finally, some numerical simulations are conducted to support analytic results.

Luteoviruses affected energy reserves and fatty acid composition of their aphid vectors

AbstractLuteoviruses are plant‐infecting RNA viruses that are transmitted by aphids in a persistent circulative mode. Luteoviruses have been shown to positively influence their aphid vectors fitness. To find out the physiological responses of aphid vectors to luteoviruses, fatty acid (FA) composition and energy components (EC) of aphid vectors including pea aphid (Acyrthosiphon pisum Harris), black bean aphid (Aphis fabae Scopoli) and bird cherry‐oat aphid (Rhopalosiphum padi L.) were evaluated in response to Pea enation mosaic virus 1 (PEMV1), Bean leafroll virus (BLRV) and Barley yellow dwarf virus‐PAV (BYDV‐PAV), respectively. Our results showed that the number and the proportion of FA of total lipid are altered in aphid vectors in response to the luteoviruses. Compared to non‐viruliferous (NV) aphids, BLRV and PEMV1 elevated the amount of myristic acid (1.13 and 1.03‐fold increase) in A. fabae and A. pisum, respectively. V R. padi individuals exhibited a 1.11‐fold increase in palmitic acid content compared to the NV individuals. In contrast, other V aphids showed a reduced proportion of FA in response to the viruses. These changes in FA profile enhanced the ratio of saturated to unsaturated FA in V aphids (4.09‐fold increase). BLRV decreased protein and lipid contents in its aphid vector, A. fabae, while carbohydrate content was found to increase in V R. padi and A. pisum. Thus, our results demonstrate that luteoviruses change the content of some FA and EC in their aphid vectors highlighting a specific interaction among virus species, plant host and aphid vector.