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Togolese Humboldt Fellow chose JKI for his Research on RNAi-Pest Control

Alexander von Humboldt Foundation sponsors the research project of Dr. Ayaovi Agbessenou. The plant protector and entomologist wants to find components for an eco-friendly RNAi-Spray to control American Tomato Pinworm. We wanted to know what drives him.

Dr. Ayaovi Agbessenou wants to find a way to control South American Tomato Pinworm Phthorimaea absoluta (formerly known as Tuta absoluta). Therefore, he already had a closer look on systemic plant-resistance mechanisms against Phthorimaea absoluta mediated by plant microbiome during his doctoral research at the International Centre of Insect Physiology and Ecology (icipe) in Kenya under the supervision of Dr. Komivi Akutse and Dr. Fathiya Khamis and Prof. Abdullahi Yusuf.

After completing his doctorate in 2023 at the University of Pretoria in South Africa, his path led him straight to the JKI-Institute for Biological Control. Arriving in April 2023 he now wants to use his two years as Postdoc Georg Forster fellow to investigate the potential of an eco-friendly, RNAi-based plant protection.

As receiving a fellowship is both - an award for the fellow's research and an honor for the host institution – we wanted to know what drives the Togolese scientist.

1. Mr. Agbessenou, we are curious: How come that you are doing research in the agricultural sector? Do you have farming background?

Yes, I am a farmer and I am from Ounabè in Akposso, a part of Togo where we grow fonio (Ed.: ancient, African cereal), coffee, cocoa, banana and several vegetables and cereal crops. I inherited the passion for farming from my father. As I grew older I decided to do a major in Agronomy - I want to contribute to the transformation of our agricultural production system.

2. Your doctorate already dealt with American Tomato Pinworm, now you are using your PostDoc to do further research on it. Why are you so interested in this pest insect?

Phthorimaea absoluta has become the biggest biotic threat to tomato production on the African continent – only by accidental introduction to Africa in 2008. The invasive insect is difficult to control and jeopardizing the livelihoods of millions of growers and other stakeholders along the crop value chain across the continent, including my native country Togo.

In response to this challenging situation, smallholder vegetable farmers have been desperately applying cocktails of synthetic pesticides to reduce the pest infestation. Yet, the indiscriminate use of synthetic insecticides has rarely delivered a satisfactory level of control due to the cryptic feeding behavior of the pest’s larval stages and the rapid development of resistance to different insecticides.

Moreover, there is growing public concern about effects on non-target organisms, environmental and human health. Thus, there is an urgent need to develop and implement alternative pest management methods.

3. You are doing research on the relatively new approach of RNAi-based pest control in crop plants. What is RNAi and how does it work? How do you want to use it in American Tomato Pinworm?

RNAi stands for “RNA interference” also referred to as “RNA silencing” – the mechanism is naturally occurring in cellular defense systems. Viruses for example may produce “hostile” dsRNA in order to modify the genome of their host cells and force them to produce virus protein. Whereas cells of the host organism will seek to suppress the mechanism.

Infected cells will use another form of RNA (siRNA) that is complementary to hostile RNA by binding and blocking it – RNA interference. Moreover, RNAi-mechanisms play a crucial role in suppressing gene-expression in organisms as well. Therefore, the idea of using RNAi in crop protection is to use highly sequence specific RNA to silence or block essential genes in a pest organism.

For Phthorimaea absoluta, we especially want to target the most destructive larval stage. Targeting genes that are essential for the insect’s growth, like development or reproduction, will have lethal consequences for the organism. As RNAi-mechanisms are highly specific to an organism’s genome, we should be able to control pest organisms very selectively, without having adverse effects on non-target species.

4. And when did you first hear about JKI and decided to work with us during your funding period?

The first time I heard about JKI was in 2012 when I was conducting my undergraduate research at the International Institute of Tropical Agriculture (IITA). Under the mentorship of Prof. Agbeko Tounou and Dr. Manuele Tamò, I conducted research on the biological control of the legume pod borer, Maruca vitrata, a key pest of cowpea. However, Prof. Christian Borgemeister from the Center for Development Research (ZEF) in Bonn and likewise my host has officially introduced me to Prof. Johannes Jehle in 2021. Both finally approved my research proposal.

I wanted to work with the Institute for Biological Control as it has considerable experience in sustainable management of insect pests with economic importance. Beyond that, it holds comprehensive experience in the development of insecticidal gene silencing technology that – in my eyes - may revolutionize insect pest control. I find it rewarding to develop biological control methods against Phthorimaea absoluta in a multidisciplinary team and thereby contributing to reduce the use of chemical pesticides. One of my goals is also – through the support of the institute - to develop and apply the most recent and most powerful gene silencing technologies, which will be of benefit to my home country.

For me it's about poverty alleviation and improving food and nutrition security in Africa and beyond – one part of the puzzle is to develop the best integrated pest management options and be able to apply them in the following.

5. The Institute is located in a quite pitoresque fruit and wine-growing area in Germany. What do you like most about the region Dossenheim/Heidelberg?

I live in Mannheim with my family and so far, we spend great moments together. There are several beautiful places in Mannheim and our favorite spot is the water tower. I really like the beautiful landscape that prevails in Dossenheim and Heidelberg. Heidelberg is known for its famous renaissance castle, which my family and I already visited.


More information on dispersal, biology and control options of Phthorimaea absoluta here: CABI Digital Library - Tomato Leafminer Portal

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