Sébastien Boquel

Assessing aphids potato virus Y-transmission efficiency: A new approach.

In order to develop an alternative method to optimize the relative efficiency factor (REF) assessment, the efficiency of transmission of Potato virus Y (PVY) by seven aphid species was examined. In vitro micropropagated potato plantlets were used to experiment on phenotypically and genetically homogeneous material. Species-specific acquisition access period (AAP) on a PVY-infected plantlet was assessed for each aphid species using electrical penetration graph (EPG) technique. Aphid probing behaviour determined by EPG showed that Macrosiphum euphorbiae and Myzus persicae exhibited the shortest AAPs (15 and 11min, respectively) whereas Rhopalosiphum padi, Sitobion avenae, Brevicoryne brassicae and Acyrthosiphon pisum exhibited the longest ones (more than 30min). The transmission rate obtained for M. persicae (83.3%) was higher than the ones reported in the literature. REFs assessment showed that A. pisum and B. brassicae were poor efficient vectors while M. euphorbiae and S. avenae seemed to be efficient ones even though their respective REF were significantly lower than that of M. persicae. The species R. padi and A. fabae did not transmit PVY. The hypothesis assessed for M. euphorbiae and S. avenae and consisting in the compensation of a weak PVY-transmission efficiency by a higher number of vectors, was not supported. The use of this new method for REF evaluation and the need to consider aphid behaviour for such an assessment was discussed.

Modulation of Aphid Vector Activity by Potato virus Y on In Vitro Potato Plants

The effects of the infection of potato (Solanum tuberosum) plants by the nonpersistent Potato virus Y (PVY) were studied on the host plant colonization behavior of different colonizing (Myzus persicae) and noncolonizing (Aphis fabae, Brevicoryne brassicae, and Sitobion avenae) aphid species. The underlying questions of this study were to know how aphids respond when faced with PVY-infected plants and whether plant infection can modify the aphid behavior involved in PVY spread. Short-range orientation behavior was observed using a dual-choice set-up and aphid feeding behavior was monitored using the electrical penetration graph technique. None of the aphid species discriminated between healthy and PVY-infected plants. Nevertheless, most individuals of M. persicae landed on and probed only in one plant whereas noncolonizing aphid species exhibited interplant movements. Study of the aphid feeding behavior showed that PVY infection essentially modified phloem and xylem ingestion. M. persicae and S. avenae exhibited an increased duration of phloem phases on PVY-infected plants whereas A. fabae showed a decreased duration of phloem phases that benefited from an increased duration of xylem ingestion phases. None of these parameters were changed in B. brassicae. These data present evidence that aphids can respond to plants infected by nonpersistent viruses. Such behavioral modifications are discussed within the context of PVY spread in potato crops.

Divergent effects of PVY-infected potato plant on aphids

Host plant selection by aphids can be positively or negatively affected when plants are infected by phytoviruses. Potato plants infected by Potato virus Y (PVY), a non-persistent virus, are reported to affect settling behaviour and growth parameters of Myzus persicae Sulzer and Macrosiphum euphorbiae Thomas. Using the Electrical penetration graph system (EPG), we demonstrated that PVY-infection of potato plants influences the feeding behaviour of these two aphid species. Myzus persicae exhibited increased phloem sap ingestion and reduced non-probing duration. Macrosiphum euphorbiae showed delayed stylet insertion, reduced activity in the phloem vessels and an enhanced non-probing duration. In addition, we showed that these two species exhibited different transmission rates. The opposite effects of PVY-infected potato plant on these two aphids are discussed in terms of PVY spreading in the field.

Effect of insecticide-treated potato plants on aphid behavior and potato virus Y acquisition

BACKGROUND The objective was to assess the effect of two contact insecticides, lambda-cyhalothrin and flonicamid, and three systemic insecticides, pymetrozine, dimethoate and imidacloprid, on the behavior and potato virus Y (PVY) acquisition of three aphid species, Macrosiphum euphorbiae (Thomas), Rhopalosiphum padi L. and Aphis fabae (Scopoli). RESULTS At 1-4 days after application, contact insecticides strongly modified aphid behavior and intoxicated them. Dimethoate sprayed on potato plants did not change the behavior of the three tested aphid species, while imidacloprid slightly reduced the probing behavior of M. euphorbiae and intoxicated several R. padi. The residual effect of the insecticides (10-21 days after application) was almost non-existent. No intoxication was found, and only slight changes in the behavior of R. padi and A. fabae were observed. The acquisition of PVY by R. padi was reduced on lambda-cyhalothrin- and dimethoate-treated plants that were sprayed a few days before the test. CONCLUSION One systemic and two contact insecticides were effective at intoxicating aphids and reducing probing behavior soon after application. Some insecticides might sporadically reduce the spread of PVY either by modifying the behavior or reducing PVY acquisition, but their action is likely limited to a short period of time after application.

Aphid Feeding Behavior in Relation to Potato Virus Y (PVY) Acquisition

ABSTBACT Potato virus Y (PVY) is transmitted by aphids in a nonpersistent manner and aphid species differ in their ability to transmit PVY. During host selection, aphids will land and probe on nonhost plant species and this behavior is an important component of the epidemiology of many aphid-transmitted viruses. In this study, we hypothesized that host selection behavior varies between aphid species and the host or nonhost status of the plant and this behavior will modulate their ability to acquire PVY. Three potato colonizers, Myzus persicae (Sulzer),Macrosiphum euphorbiae (Thomas), and Aphis nasturtii (Kaltenbach) and three casual visitors to potato fields, Myzus cerasi (F.), Rhopalosiphum padi (L.), and Sitobion avenae (F.) were evaluated using two acquisition assays. In one assay, the normal host selection and feeding behavior of aphid species were eliminated using an artificial diet while the other considered the normal host selection and feeding behavior of aphid species on potato plants. PVY acquisition rates of aphid species widely differed between the two assays indicating the impact of host selection and feeding behavior on PVY acquisition. This behavior varied greatly between potato colonizers and noncolonizers. We recommend that laboratory evaluations of PVY vector efficiency consider the normal host selection and feeding behavior of aphid species on potatoes.

Quantification of mineral oil accumulation and movement in potato plants and its significance in potato virus Y management

BACKGROUND Mineral oils are increasingly sprayed to manage potato virus Y (PVY). However, the mode of accumulation and movement of mineral oil in the potato plant has not been understood. This information is important for optimisation of the concentration and frequency of spraying. During the 2012 season, cvs Russet Burbank and Shepody were planted in the field and in the greenhouse, respectively, and were subjected to mineral oil treatments. The plant samples from the treatment plots were collected, and oil was extracted and quantified using gas chromatography-mass spectrometry. RESULTS Mineral oil stayed in the vicinity of the sprayed leaves and did not move from leaflet to leaflet or from leaflet to stem, stolon, tuber or root. Following spraying, the oil content in the plant leaves diluted as time progressed. At plant maturity, leaves sampled from the greenhouse sprayed plants had about 4 times more oil content than those sampled from the field sprayed plants. Plots treated with regular spray of mineral oil showed low PVY incidences at crop harvest. CONCLUSION The information generated in this study on the pattern of accumulation and movement of mineral oil in greenhouse- and field-grown potato plants shows that, as the oil does not move from leaflet to leaflet, frequent mineral oil sprays from crop emergence to harvest are required to prevent PVY infection in newly emerged leaflets and seasonal spread of PVY. The frequency of sprays may be kept higher from early to mid-stage, when plant growth is faster, and lower close to plant maturity.

Vector activity of three aphid species (Hemiptera: Aphididae) modulated by host plant selection behaviour on potato (Solanales: Solanaceae)

Summary Viral diseases non-persistently transmitted by aphids are of great economic importance in several annual crops. Transmission efficiency of these non-persistent phytoviruses is dependant on vector efficiency (i.e. vector intrinsic ability to transmit the virus) but also on the vector activity that implies the early steps of aphid host plant selection process (i.e. brief intracellular stylet punctures after landing) and to their interplant movement ability. In Europe, Macrosiphum euphorbiae (Thomas 1878) is considered as one of the most serious virus vectors on potato (Solanum tuberosum L. 1753). Nevertheless, several alate aphid species that do not colonise potato plants are trapped in potato crops. Therefore, we investigated, through laboratory experiments, vector activity of one potato colonising aphid, M. euphorbiae, and two non-colonising potato aphids, the bird cherry-oat aphid Rhopalosiphum padi (L. 1758) and the pea aphid Acyrthosiphon pisum (Harris 1776). A settling experiment was used to evaluate dispersal activity, and the electrical penetration graph (EPG) technique was used to investigate probing activity on potato plants. Results showed that M. euphorbiae exhibited a better vector activity than other two aphid species in terms of landing and probing. By contrast, interplant movements were only recorded on non-colonising aphids, suggesting a better vector activity than M. euphorbiae in terms of locomotive behaviour. These data confirm the involvement of A. pisum and R. padi in the spread of non-persistent viruses.

Detection of Potato virus Y from the stylets of a single aphid by one-step reverse transcription polymerase chain reaction

Detection of Potato virus Y from the stylets of a single aphid by one-step reverse transcription polymerase chain reaction Jianhua Zhang, Xianzhou Nie, Upeksha Nanayakkara, S ebastien Boquel, Marie Andr ee Gigu ere & Yvan Pelletier* Department of Biology, University of New Brunswick, PO Box 4400, Fredericton, New Brunswick, Canada E3B 5A3, Potato Research Center, 850 Lincoln Rd, Fredericton, New Brunswick, Canada E3B 4Z7, and Comit e Nord Semences, Innovation, Protection, Recherche, Environnement (SIPRE), Rue des Champs Potez, Achicourt 62217, France

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

Abstract 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.

Mineral Oil Inhibits Movement of Potato Virus Y in Potato Plants in an Age-Dependent Manner

Potato Virus Y (PVY) is one of the most devastating pathogens threatening potato production worldwide. It is a RNA virus that is disseminated by aphids in a non-persistent manner. Regular application of mineral oil on potato fields is known to reduce the number of PVY-positive tubers in post-harvest testing. The mechanism of this phenomenon is not well understood, but it is hypothesized to influence the virus-vector-plant relationships. Here, we present data from greenhouse and field trials that shed light on the effect of mineral oil on local and systemic accumulation of PVYO in susceptible Shepody and Russet Burbank. The data suggests that mineral oil did not influence PVYO levels in mechanically-inoculated leaves nor tubers of plants with a secondary infection. However, a reduction in systemic PVYO levels was observed in mineral oil-treated older plants but not in younger plants, suggesting that mineral oil inhibits PVYO movement in an age-dependent manner.ResumenEl virus Y de la papa (PVY) es uno de los patógenos más devastadores que amenazan la producción de papa en todo el mundo. Es un virus de ARN que se disemina por áfidos de manera no persistente. Se sabe que la aplicación regular de aceite mineral en campos de papa reduce el número de tubérculos positivos a PVY en pruebas de poscosecha. El mecanismo de este fenómeno no está bien entendido, pero se tiene la hipótesis de que ejerce una influencia en la relación virus-vector-planta. Aquí presentamos datos de ensayos de invernadero y campo que arrojan luz sobre el efecto del aceite mineral en la acumulación local y sistémica de PVY-O en las susceptibles Shepody y Russet Burbank. Los datos sugieren que el aceite mineral no influenció los niveles de PVY-O en hojas inoculadas mecánicamente ni en los tubérculos de plantas con infección secundaria. No obstante, se observó una reducción en los niveles sistémicos de PVY-O en plantas viejas tratadas con el aceite mineral pero no en las jóvenes, sugiriendo que el aceite mineral inhibe el movimiento de PVY-O de manera dependiente de la edad.