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Salim Bourras

Salim Bourras
For a sustainable future without pesticides and antibiotics.


We are investigating how pathogens cause disease by interacting with their host(s) and other pathogens from the local pathobiome. We are focusing on interactions between fungal pathogens, and the particular role of mobile molecules such as effectors, antimicrobial proteins, and small RNAs in regulating disease interactions, as well as the role of immune receptors in regulating tradeoffs in host immune responses. We aim at producing translation research that probes fundamental aspects of microbe-microbe and host-microbe interactions to set the ground for a wide range of applications ranging from antimicrobial resistance to resistance breeding.

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- Advanced Master Course in Plant Pathology [Course Leader - Teacher - Examiner]  ¦ Swedish University of Agricultural Sciences (Uppsala. Sweden).

- NOVA PhD Course Epidemiology and Populations Genetics [Teacher] ¦ Norwegian University of Life Sciences (Honne, Norway).

- Advanced Master Course Mechanisms of Plant Disease Resistance Against Fungal Pathogens [Teacher - Examiner] ¦ University of Zurich (Zurich, Sweitzerland)

- Master Course Methods in Molecular Biology [Teacher] ¦ University of Zurich (Zurich, Sweitzerland).

- Introduction to Fundamental Biology [Teacher] ¦ Pierre et Marie Curie Faculty of Medicine. St Antoine Hospital (Paris. France).

- Metabolic Biochemistry Practical Course [Teacher] ¦ University of Versailles St-Quentin-en-Yvelines (Versailles. France).



The plant rhizosphere and phyllosphere are taxonomically rich habitats for a variety of microorganisms competing for the same limited resources. Our first line of research aims at understanding the molecular mechanisms that pathogens have evolved to outcompete the local pathobiome, and persist in nature. The first answer to this question can be traced back to Alexander Fleming’s discovery of Benzylpenicillin (Penicillin), a substance produced by the Ascomycete fungus Penicillium chrysogenum primarily employed to outcompete bacteria for food sources. Considering the ecological role of antibiotics, our work and the work of others suggest there is a much larger diversity of antimicrobial agents and strategies employed by fungi to interact with their environment and other organisms. Our work focuses on the antimicrobial interactome of plant colonizing fungi, and the specific contribution of cross-kingdom molecular mobility provided by small RNAs, effectors proteins, and antimicrobial proteins, to the establishment and resilience of stable pathobiomes.

The recommendations of the EU plan on antimicrobial resistance (AMR) recognize the importance ‘to boost the development of new antimicrobials’ and to improve our ‘understanding of the mechanisms causing resistance’. Our research will lead to the discovery a larger diversity of antimicrobial proteins that have not been characterized before, while the molecular studies of their mode of action on plant and animal pathogens (in collaboration with colleagues from SLU BioC and VH with complementary expertise), will improve our understanding of a larger variety of gain of resistance mechanisms and how to mitigate them.


Our second line of research aims at understanding the contribution of pathogen-pathogen interactions to the regulation of multi-pathogen resistance. Immunity is costly. When the immune system is activated, plants have to make lifesaving decisions as to what resistance gene goes first (timing and prioritization), where it must be expressed (tissue specificity), how long and how strong it is must expressed (energy cost). An additional layer of complexity is provided by the fact that resistance to different, simultaneously occurring diseases might require diametrically opposed immune responses thus leading to important tradeoffs. There is increasing evidence suggesting that pathogens have evolved the capacity to highjack these tradeoffs, while in other cases, interference between host’s immune receptors has been reported.

A sustainable future of our food system relies on our capacity to create healthy crops that can genetically withstand disease without the use of fungicides or antibiotics. The primary source of resistance traits/genes available to us is agricultural biodiversity, which has been recognized as an endangered natural resource that ‘must be used rationally and wisely’ by the FAO, and the UN SDGs. Our research aims at identifying, and isolating the genetic factors mitigating resistance tradeoffs in plants based on the study of the plant immune response to simultaneous infections with multiple pathogens. Such discovery will be instrumental for designing the healthy crops of the future.


#Prof. Beat Keller. Department of Plant and Microbial Biology. University of Zürich. Switzerland.

#Dr. Thomas Wicker. Department of Plant and Microbial Biology. University of Zürich. Switzerland.

#Prof. Bruce McDonald. Department of Environmental Systems Science. ETH Zurich. Switzerland.

#Dr. Andrea Sanchez-Vallet. Centre for Plant Biotechnology and Genomics. Universidad Politécnica de Madrid. Spain.

#Dr. Kostya Kanyuka. Biointeractions and Crop Protection. Rothamsted Research. UK.

#Dr. Roi Ben David. Institute of Plant Sciences. Agricultural Research Organization. Israel.

#Dr. Barend Wentzel. Small Grain Institue. Agricultural Research Council. South Africa.

#Dr. Kartik Baruah. Department of Animal Nutrition and Management. Swedish University of Agricultural Siences. Uppsala. Sweden.


#PhD in Biology [2012]. Université Paris Sud 11. France.

#MSc Life Science and Technology [2008]. AgroParisTech School of Engineering. Paris. France.


Direct Supervisor

{PhD Students}

1# Kaitlin McNally. University of Zurich. Switzerland. [Prof. Beat Keller Group]

2# Coraline Praz. University of Zurich. Switzerland. [Prof. Beat Keller Group]

3# Luisa Schaefer. University of Zurich. Switzerland. [Prof. Beat Keller Group]

4# Stefan Lindner. University of Zurich. Switzerland. [Prof. Beat Keller Group]

5# Marion Müller. University of Zurich. Switzerland. [Prof. Beat Keller Group]

6# Lukas Kunz. University of Zurich. Switzerland. [Prof. Beat Keller Group]

7# Jonathan Isaksson. University of Zurich. Switzerland. [Prof. Beat Keller Group]

{MSc Students}

8# Kaitlin McNally. University of Zurich. Switzerland. [Prof. Beat Keller Group]

9# Coraline Praz. University of Zurich. Switzerland. [Prof. Beat Keller Group]

10# Luisa Schaefer. University of Zurich. Switzerland. [Prof. Beat Keller Group]

11# Carol Kaelin. University of Zurich. Switzerland. [Prof. Beat Keller Group]

{BSc Students}

12# Ayano Tanaka. SLU - Sweden.

{Research Engineers and Technicians}

13# Simon Flueckiger. University of Zurich. Switzerland. [Prof. Beat Keller Group]

14# Michael Schlaefli. University of Zurich. Switzerland. [Prof. Beat Keller Group]

15#Lukas Kunz. University of Zurich. Switzerland. [Prof. Beat Keller Group]


Joint Supervisor

{PhD Students}

16# Manuel Poretti - University of Zurich. Switzerland [Dr. Thomas Wicker]

17# Carol Kälin - SLU. Sweden [Dr. Magnus Karlsson]


18# Shirin Akhtar [Postdoc] - SLU. Sweden [Dr. Anna Berlin]


Selected publications


19# Lindner S, Keller B, Pal Singh S, Hasenkamp Z, Jung E, Müller MC, Bourras S¤ and Keller B¤ (2020). Single residues in the LRR domain of the wheat PM3A immune receptor can control the strength and the spectrum of the immune response. The Plant Journal. ¤ corresponding author. [in press]

18# Schaefer LK, Parlange F, Buchmann G, Jung E, Wehrli A, Herren G, Müller MC, Stehlin J, Schmid R, Wicker T, Keller B and Bourras S¤ (2020). Cross-kingdom RNAi of pathogen effectors leads to quantitative adult plant resistance in wheat. Frontiers in Plant Science. Doi: 10.3389/fpls.2020.00253. ¤corresponding author.


17# Poretti M, Praz C, Meile L, Kälin C, Schaefer LK,  Schläfli M, Widrig V, Sanchez Vallet A, Wicker T and Bourras S¤ (2019). Domestication of high-copy transposons underlays the wheat small RNA response to an obligate pathogen. Molecular Biology and Evolution. ¤ corresponding author.

16# Bourras S*¤, Kunz L*, Xue M*, Praz CR, Müller MC, Kälin C, Schläfli M, Ackermann P, Flückiger S, Parlange F, Menardo F, Schaefer LK, Ben David R, Roffler S, Oberhaensli S, Widrig V, Lindner S, Isaksson S, Wicker T, Yu D¤ and Keller B¤ (2019). The AvrPm3-Pm3 effector-NLR interactions control both race-specific resistance and host-specificity of cereal mildews on wheat. Nature Communications. DOI: 10.1038/s41467-019-10274-1. *joint first authors, ¤corresponding authors.


15# Sánchez-Martín J, Bourras S and Keller B (2018). Diseases affecting wheat and barley: powdery mildew. Integrated disease management of wheat and barley. Burleigh Dodds Science Publishing. doi: 10.19103/AS.2018.0039.04. [BOOK CHAPTER]

14# Müller MC, Praz CR, Alexandros GS, Menardo F, Kunz L, Schudel S, Oberhänsli S, Poretti M, Wehrli A, Bourras S, Keller B and Wicker T (2018). A chromosome-scale genome assembly reveals a highly dynamic effector repertoire of wheat powdery mildew. New Phytologist 221:2176-2189. doi:DOI:10.1111/nph.15529.

13# Bourras S, Praz CR, Spanu PD and Keller B (2018). Cereal powdery mildew effectors: a complex toolbox for an obligate pathogen. Current Opinion in Microbiology 46:26-33. doi: 10.1016/j.mib.2018.01.018.

12# Praz CR, Menardo F, Robinson MD, Müller MC, Wicker T, Bourras S¤ and Keller B¤ (2018). Non-parent of origin expression of numerous effector genes indicates a role of gene regulation in host adaption of the hybrid triticale powdery mildew pathogen. Frontiers in Plant Science 9:49. doi: 10.3389/fpls.2018.00049. ¤corresponding authors.

11# McNally KE, Menardo F, Lüthi L, Praz CR, Müller MC, Kunz L, Ben-David R, Chandrasekhar K, Dinoor A, Cowger C, Meyers E, Xue M, Zeng F, Gong S, Yu D, Bourras S¤and Keller B¤ (2018). Distinct domains of the AVRPM3A2/F2 avirulence protein from wheat powdery mildew are involved in immune receptor recognition and putative effector function. New Phytologist 218:681-695. doi: 10.1111/nph.15026. ¤corresponding authors.


10# Praz CR*, Bourras S*, Zeng F, Sánchez-Martín J, Menardo F, Xue M, Yang L, Roffler S, Böni R, Herren G, McNally KE, Ben-David R, Parlange F, Oberhaensli S, Flückiger S, Schäfer L, Wicker T, Yu D and Keller B (2017). AvrPm2 encodes an RNase-like avirulence effector which is conserved in the two different specialized forms of wheat and rye powdery mildew. New Phytologist 213:1301-1314. doi: 10.1111/nph.14372. *joint first authors.

9# Meyer M, Bourras S, Gervais J, Labadie K, Cruaud C, Balesdent M-H, Rouxel T. (2017) Impact of biotic and abiotic factors on the expression of fungal effector-encoding genes in axenic growth conditions. Fungal Genetics and Biology 99:1-12. doi: 10.1016/j.fgb.2016.12.008

8# Feehan JM, Scheibel KE, Bourras S, Underwood W, Keller B and Somerville SC. (2017) Purification of High Molecular Weight Genomic DNA from Powdery Mildew for Long-Read Sequencing. JoVE. 31:121. doi: 10.3791/55463.


7# Bourras S, McNally KE, Müller MC, Wicker T and Keller B. (2016) Avirulence genes in cereal powdery mildews: the gene-for-gene hypothesis 2.0. Frontiers in Plant Science 7:241. doi:10.3389/fpls.2016.00241.

6# Menardo F, Praz CR, Wyder S, Ben-David R, Bourras S, Matsumae H, McNally KE, Parlange F, Riba A, Roffler S, Schaefer LK, Schimizu KK, Valenti L, Zbinden H, Wicker T and Keller B. (2016) Hybridization of powdery mildew strains gives rise to pathogens on novel agricultural crop species. Nature Genetics 48(2):201-205. doi: 10.1038/ng.3485.


5# Bourras S*, McNally KE*, Ben-David R, Parlange F, Roffler S, Praz CR, Oberhaensli S, Menardo F, Stirnweis D, Frenkel Z, Schaefer LK, Flückiger S, Treier G, Herren G, Korol AB, Wicker T and Keller B. (2015) Multiple avirulence loci and allele-specific effector recognition control the Pm3 race-specific resistance of wheat to powdery mildew. Plant Cell 27: 2991-3012. doi: 10.1105/tpc.15.00171. *joint first authors.

4# Bourras S, Rouxel T, Meyer M. (2015) Agrobacterium tumefaciens Gene Transfer: How a plant pathogen hacks the nuclei of plant and nonplant organisms. Phytopathology 105:1288-301. doi: 10.1094/PHYTO-12-14-0380-RVW.

3# Parlange F, Roffler S, Menardo F, Ben-David R, Bourras S, McNally KE, Oberhaensli S, Stirnweis D, Buchmann G, Wicker T and Keller B. (2015) Genetic and molecular characterization of a locus involved in avirulence of Blumeria graminis f. sp. tritici on wheat Pm3 resistance alleles. Fungal Genetics and Biology. 82:181-92. doi: 10.1016/j.fgb.2015.06.009.


2# Bourras S, Meyer M, Grandaubert J, Lapalu N, Fudal I, Linglin J, Ollivier B, Blaise F, Balesdent M-H and Rouxel T. (2012). Incidence of genome structure, DNA ssymmetry, and cell physiology on T-DNA integration in chromosomes of the phytopathogenic fungus Leptosphaeria maculans. G3: Genes,Genomes,Genetics 2:891-904

1# Rouxel T, Grandaubert J, Hane JK, Hoede C, van de Wouw AP, Couloux A, Dominguez V, Anthouard V, Bally P, Bourras S et al. (2011) Diversification of effectors within compartments of the Leptosphaeria maculans genome affected by RIP mutations. Nature Communications 2: 202.


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Associate Senior Lecturer at the Department of Forest Mycology and Plant Pathology; Division of Plant Pathology/Epidemiology
Telephone: +4618-671617
Postal address:
Skoglig mykologi och växtpatologi , Box 7026
750 07 UPPSALA
Visiting address: Almas Allé 5, Uppsala