Peach - Myzus persicae interactions as controlled by winter pruning and nitrogen fertilization: from experimental analysis to modeling

Introduction: The research purpose is the management of the peach–Myzus persicae system, by integration of chemical, biological and cultural pest control methods. We used a modeling approach to address it. To assist model development, we first aim to experimentally characterize peach–aphid interactions driven by winter pruning and nitrogen (N) fertilization, proposed as potential cultural control methods. Methods: We artificially infested peach trees with aphids and applied various levels of pruning intensity (from 0 to 80%) and N treatments (from shortage to overdose). Aphid dynamics, foliar growth, fruit yield and quality were monitored. Results: Aphid infestation of peach trees increased with increasing pruning intensity because of an exponential increase of the proportion of growing shoots at the expense of short shoots, aphids having developed better on growing shoots. According to the N gradient, plant vigor increased then leveled off while aphid abundance increased then decreased. Plant vigor partially explained aphid performance that exhibited a significant nonlinear response to leaf N content. Preliminary analyses of foliar chemistry (free amino-acids, phenolic and cyanogenic compounds) gave elements to explain this response at N shortage but not at N overdose. Aphids induced premature defoliation on growing shoots and reduced their growth. Following infestation, trees had compensatory growth. Aphids did not significantly reduce fruit mass and refractometric index. Conclusions: Winter pruning and N fertilization can be used to control aphids; application in production orchards is discussed. We illustrate the potential of a simulation model, incorporating these results, to investigate alternative strategies for crop-pest management

Volatile organic compound emissions induced by the aphid Myzus persicae differ among resistant and susceptible peach cultivars and a wild relative

International audienceLittle is known on aphid-induced emissions of volatile organic compounds (VOCs) from trees and particularly on their intraspecific variability in association with resistance traits. We compared VOC emissions from five peach cultivars (Prunus persica (L.) Batsch) and a wild relative (Prunus davidiana (Carrière) Franch) that differ in their level (susceptible/resistant) and type (antixenosis, antibiosis) of resistance to the green peach aphid, Myzus persicae (Sulzer). Additionally, the kinetics of VOC induction in response to aphids was compared with that by mechanical wounding. Qualitative and overall quantitative differences among peach genotypes were found in VOC emissions that were mainly composed of methyl-salicylate, farnesenes, (E)-β-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene. Irrespective of the type of resistance, all resistant genotypes had increased VOC emissions upon aphid attack, while in susceptible genotypes emissions remained low. Emission increases were highest in the genotypes that express increased aphid resistance during second infestations, which had also the highest proportions of methyl-salicylate in their emissions. VOC induction by aphids proceeded slowly with a delay of several hours. Artificial wounding of leaves did not result in emissions of aphid-induced VOCs but caused an immediate burst of green leaf volatiles and benzaldehyde. We conclude that VOC induction in resistant peach cultivars is part of a general defence syndrome that is being avoided or suppressed by M. persicae in the susceptible genotypes. The induction likely involves an aphid-specific elicitor and (methyl)-salicylate in the subsequent signalling and regulation processes that should include gene activation due to the marked delay in the emission response. The results are compared with those of the literature and discussed in view of their ecological and environmental significanc

Variability in odour emissions induced by the aphid Myzus persicae among peach cultivars and a wild related species expressing different types of resistance

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Evaluation of integrated management scenarios of the peach tree – Myzus persicae system using a crop-pest model

National audienceIntegrated Fruit Production (IFP) calls for an adaptation of production processes to improve crop quality and environmental safety. This approach gives priority to alternative methods of pest control. Our study investigates the potential of management scenarios that integrate chemical, biological (inundative release of Harmonia axyridis ladybirds) and cultural (nitrogen fertilization and winter pruning) pest control methods for the peach tree-aphid system. We used a modeling approach to address this question. We defined 108 management scenarios, which were based on theoretical pest control strategies combined with control variables relative to pest control and cultural practices. Then, we performed model simulations of these scenarios and studied the relationships between control variables and model outputs referring to agronomical, economical, sanitary (pest), and sustainability performance. Results showed that ‘agronomical performance’ was largely controlled by ‘agronomical practices’, while ‘pest performance’ was largely controlled by ‘pest control practices’

Metabolic profiling of shoot apices infested by the peach-potato aphid in susceptible and resistant peach cultivars

International audience1H NMR and targeted HPLCs were used to analyse the response of peach (Prunus persica L. Batsch) to infestation by the peach-potato aphid (Myzus persicae Sulzer, PPA). The response was studied in “Rubira”, a red-leaf cultivar resistant to PPA (Pascal et al, 2002) that shows strong level of induced resistance two days after infestation (Sauge et al, 2002) and “GF305”, a susceptible cultivar. Growing shoot apices, that are the preferred settling and feeding site of PPA, were sampled 48 hours after infestation and analysed for their 1H NMR profiles and their levels of main primary and secondary metabolites. Whereas no obvious differences were detected between metabolic profiles of infested and non-infested plants in the “GF305” susceptible cultivar, clear-cut changes in the 1H NMR and HPLC profiles were observed in Rubira following infestation. Carbohydrates and most organic acids showed a marked decrease. Several amino acids, including lysine and branched-chain and aromatic amino acids, showed a large accumulation whereas levels of glutamine, proline and threonine were greatly reduced. Infestation of Rubira by PPA also triggered accumulation of secondary metabolites, including phenolic and cyanogenic compounds. This first metabolomic approach of plant responses to infestation by an aphid species provides new insights into the metabolic pathways affected by insect feeding. Hypotheses on the mechanisms involved in induced resistance are discussed

Effets de l'infestation sur le profil métabolique d'apex de variétés de pêcher sensibles et résistantes au puceron vert

National audienceLes bases fonctionnelles des interactions entre plante et insectes piqueurs suceurs tels les pucerons restent mal connues malgré l’impact de ces ravageurs en agriculture. Dans le cadre de la caractérisation fonctionnelle de l’interaction entre le puceron Myzus persicae, espèce modèle en écologie, et son hôte primaire, le pêcher (Prunus persica L. Batsch), espèce modèle pour l’étude des Rosacées, nous avons mis en oeuvre une démarche d’analyse du métabolome sur les apex de pêcher, site d’alimentation privilégié de l’insecte. Nous avons étudié, par spectroscopie de RMN du proton et analyses HPLC ciblées sur les principaux pools de métabolites primaires et secondaires hydrosolubles, les modifications de profil métabolique induites par l’infestation dans les apex de deux variétés de pêcher, sensible (GF305) ou résistante (Rubira) à M. persicae [1,2]. L’analyse en composante principale de la signature spectrale obtenue par RMN et les analyses en HPLC révèlent de profondes modifications des profils métaboliques chez la variété résistante 48 heures après l’infestation : on observe notamment une baisse de la teneur de la plupart des sucres et acides organiques, de certains acides aminés (glutamine, proline, thréonine) alors que les teneurs en acides aminés ramifiés (leucine, isoleucine, valine) et aromatiques (phénylalanine, tyrosine) et en métabolites secondaires (composés phénoliques et cyanogéniques) augmentent. Les modifications observées chez la variété sensible sont faibles et pour la plupart divergent de celles observées chez la variété résistante. Ces résultats permettent d’émettre des hypothèses sur les voies métaboliques impliquées dans la réponse à l’infestation et sur la nature des effecteurs pouvant jouer un rôle dans la résistance induite chez Rubira. Cette étude met en lumière l’apport de l’approche métabolomique pour l’étude des interactions plante – insectes piqueurs suceurs

Genetic and functional characterization of the peach - Myzus persicae interaction : towards breeding for durable resistance within integrated orchard management

National audienceIntegrated production of fruit and vegetable species is one major field of research at Avignon INRA centre. Breeding for durable resistance to the green peach aphid, Myzus persicae (Sulzer) and other enemies of peach crop (Prunus persica L. Batsch) has been initiated fifteen years ago. Several sources of resistance are available among wild and domesticated peaches. Because all resistance genitors used in these programmes are of poor agronomic value, improvement of fruit quality is a long-lasting process. In order to avoid the erosion of the level of plant resistance during this process, the detailed analysis of the underlying mechanisms was undertaken. Here, we present some aspects of the work carried out on the genetic and physiological mechanisms of peach resistance to M. persicae. In addition to the analysis of the plant-aphid interaction under the influence of plant genetic factors, the effects of technical operations, such as winter pruning or nitrogen fertilization, on the aphid population dynamics are being investigated. Varietal resistance combined to cultural practices can be considered as an ultimate strategy to increase the efficacy of aphid control in orchards