Mechanisms involved in plant resistance to the green peach aphid Myzus persicae

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The green peach aphid (GPA) Myzus persicae and other sap-feeding insects, including other aphids, whiteflies, psyllids, froghoppers, leafhoppers, planthoppers and Lygus bugs, are economically important pests worldwide. They do not only cause direct feeding damage, but also transmit more than half (> 500) of all described plant viruses and a variety of economically important plant pathogenic bacteria. A recent example is a froghopper-transmitted bacterial pathogen (Xylella fastidiosa), which is threatening olive tree plantations in Italy and may spread to other olive-growing regions in the Mediterranean (the Guardian, 8 Jan 2015). Whereas Bacillus thuringiensis (Bt) toxin transgenic crops (grown in USA, Brazil and Asia) are resistant to major pests, such as moths and beetles, Bt is not effective against sap-feeding insects. Therefore, sap-feeding insect pests have increased on these transgenic crops.GPA alone colonizes over 400 plant species of more than 50 plant families and this aphid species transmits more than 100 different plant viruses, including 6 distinct sugar beet viruses.Sap-feeding insects are predominantly controlled by extensive insecticide applications causing these insects to develop resistance to the insecticides. GPA has developed resistance to 71 different insecticides and, as such, holds the record of most insect resistances among all insects. Neonicotinoids are one of few insecticides that can effectively control GPA. However, GPA clones resistant to these chemicals have been identified in several parts of Europe. Moreover, neonicotinoids are being taken off the market owing to increasingly restrictive (EU and national) legislation fuelled by concerns of consumers about insecticide toxicity to human health and the ecosystem. Uncontrolled, GPA can reduce sugar beet yields by 45%, making this crop uneconomic in Europe. A similar fate is predicted for other crops susceptible to GPA, including oilseed rape, broccoli, cauliflower, cabbage, tomato, potato, pepper, sugar beet etc. To reduce insecticide use and safeguard the food supply in Europe and worldwide, alternative methods to control GPA and other sap-feeding insects, such as the generation of plant varieties that are resistant to GPA, are essential and need to become available in the coming few years. We anticipate that a major impact of this proposal is to make a major leap forward to achieve this goal.Approach: GPA and other insects produce virulence proteins (effectors) in their saliva that interact with plant proteins (targets) to modulate key plant processes, such as plant defense responses, that make the plants more susceptible to aphid colonization. Hence, we wish to increase plant resistance to aphids by preventing effector-target interactions through the introduction of effector-insensitive target alleles into plants using transgenic and non-transgenic approaches.If successful, this project will open up a plethora of new avenues to obtain resistance to GPA, and possibility other sap-feeding insects, of multiple economically important plant species. This project is a collaboration with SESVanderHave UK LTD (SV), a leading breeder of sugar beet varieties with a proven performance worldwide. A goal of this proposal is for SV to develop resources and technologies so that they will be in an excellent position to take advantage of the new discoveries made in this project and obtain GPA-resistance sugar beet more quickly. Currently low numbers of students are being trained in (a combination of) entomology, agriculturally important insect pests and plant breeding. Therefore, we will engage young students in our project. Since we anticipate that this project will provide an example of how plant-breeding approaches can generate sustainable resistance to insect pests, we will organize outreach activities to engage plants breeders and downstream processors of multiple crops in our approach.