Chemical Communication in Plant-Aphid Interactions

Mechanisms that maintain and separate pea aphid host races

Dr. Grit Kunert

The pea aphid, Acyrthosiphon pisum (Harris), is actually a complex of distinct races that each is specialized on a native host plant of the legume family [Peccoud, J., Ollivier, A. et al. (2009) and Peccoud, J. and J. C. Simon (2010)]. Some aphid races are able to survive on several plant species, while others only survive on just one or a few plant species. However, all pea aphid host races can develop on the universal host plant Vicia faba. This ecological specialization can be considered as one of the first steps towards sympatric speciation since the host fidelity of races leads to assortative mating which reduces gene flow between host-races. In our group we enter into the questions why some aphid races are able to feed on a certain legume plant whilst the same plant is unsuitable for another aphid race. What makes certain legume plants resistant to some aphid races? And what might aphid races force to feed on a certain legume plant?

Cooperation partners: Jean-Christophe Simon, INRA, Université Rennes, France; Alexandra Furch, FSU Jena, Department of Plant Physiology, Plant Vascular Biology Research Group

Characterizing feeding behaviour of Acyrthosiphon pisum clones on host and non-host plant species by the electrical penetration graph (EPG) technique

Alexander Schwarzkopf

Our study aims to localize plant factors which influence host fidelity and hence host race formation in A. pisum. We conducted a broad comparative study on several A. pisum clones collected from different legume host plants in France and the United Kingdom. Firstly, we characterized the performance of nine A. pisum clones on six legume plant species, and showed different degrees of specialization to potential host plant species. Secondly, we selected six aphid clones and monitored their feeding behavior on four plant species by the Electrical Penetration Graph (EPG) technique. With the differences in the feeding behavior we try to explain the different degrees of host plant specialization. Additionally, we localize plant factors influencing aphid feeding behavior in different plant tissues.

Legume chemistry and the specificity of pea aphid races

Carlos Fernando Sánchez Arcos

Each pea aphid host races is specialized on a native host plant of the legume family. The role of the host plant chemistry for this adaptation has not been studied in depth, so the main objective of this project will be the isolation, purification, identification, and evaluation of chemical compounds from Pisum sativum, Vicia faba, Medicago sativa and Trifolium pratense involved in aphid – host plant specialization.

Amino acid and sugar content of different pea aphid host plants

Susanne Seyfarth

Phloem sap is the main food source for aphids and it is dominated by sugars. In a much lesser concentration free amino acids are available. Since the concentrations of sugars and amino acids are plant species specific we will investigate the sugar and amino acid composition from phloem sap and leave extracts of the legumes Pisum sativum, Vicia faba, Medicago sativa and Trifolium pratense. When aphids feed on plants they evoke special defence reactions. We will investigate whether infestation of legume plants with different aphid races also effect the composition of amino acids and sugars in the phloem sap and leave extracts.

The role of enemy free space for the maintenance of pea aphid races

Ilka Vosteen

The pea aphid complex consist of at least 11 genetically distinct host races which are adapted to their specific host plants, but can all develop on the universal host plant Vicia faba. Natural enemies might prefer some of the host plants for prey searching or oviposition, eventually creating an enemy free space for aphids on certain host plants. The existence of such an enemy free space may be one factor which helps to maintain the separated host races of the pea aphid complex. The attractiveness of a certain plant for natural enemies might depend on host plant architecture, volatile profile and chemical composition which may alter the nutritional value and / or toxin content of aphids, thereby influencing natural enemy performance. The aim of my PhD thesis is to test if the different host plants provide a predator free or reduced space for the aphid races specialized on them and to link predator preference with certain plant traits.

Interaction between legume chemistry and facultative symbiosis

Aleksa Stanisic, Dr. Elizabeth Pringle, Dr. Grit Kunert

Our project investigates feedbacks between plant chemistry and the facultative mutualisms between pea aphids and two of their "secondary" bacterial endosymbionts (Regiella insecticola and Rickettsia sp.). Previous research has suggested that aphid genotype x symbiont genotype interactions strongly affect pea-aphid performance on the different pea-aphid host plants. We are studying how plants respond hormonally and metabolically to feeding by different pea-aphid host races experimentally infected with the same genotype of endosymbiotic bacteria, as well as how these responses ultimately affect pea-aphid performance and host-plant choice.

Former group members:

Dr. Eduardo Hatano: PhD thesis (2009): Chemical communication in an aphid-natural enemy system: new mechanisms of aphid alarm signalling and wing induction. Supervised by Prof. Wolfgang Weisser

Carolina Reinhold: Diploma thesis (2011): Der Einfluss von (E)-β-Farnesen auf das Wirtswahlverhalten von Myzus persicae

Susanne Seyfarth: Diploma thesis (2013): Der Aminosäure- und Zuckergehalt von Pflanzen in Abhängigkeit vom Blattlausbefall

Daniel Rosenberger: Technical assistant (2008-2012)