When higher aggressiveness compensates for a lack of virulence

The use of resistance genes exerts strong selective pressure on plant pathogen populations, leading to the emergence of new virulences and sometimes their widespread dissemination. Research conducted by the ADEP team at BIOGER on wheat leaf rust revealed that the frequency of virulences in the French Puccinia triticina population cannot be fully explained by the deployment of resistance genes across the landscape. The study, published in this third article from Cécilia Fontyn's thesis*, emerged from the observation that two pathotypes (defined by their combination of virulences) that dominated the French varietal landscape between 2012 and 2015 were present at equivalent frequencies, despite the theoretical advantage conferred to one of them (166 317 0) by its virulence to the Lr3 gene, while the other (106 314 0) was avirulent. Isolates representing the most frequent genotype within the 106 314 0 pathotype (G2) were more aggressive than those representing the second pathotype (166 317 0, G1), for all three components tested on seedlings in the greenhouse: infection efficiency, latency period, and sporulation capacity. These unprecedented experimental results demonstrate that aggressiveness can compensate for the lack of virulence to a major resistance gene and can play a significant role in the evolution of pathogen populations.

* Cécilia Fontyn defended her thesis on November 8, 2022, under the supervision of Henriette Goyeau, Frédéric Suffert, and Thierry Marcel.

Fontyn C, Meyer KJG, Boixel A-L, Picard C, Destanque A, Marcel TC, Suffert F, Goyeau H. 2024. Can higher aggressiveness effectively compensate for a virulence deficiency in plant pathogen? A case study of Puccinia triticina’s fitness evolution in a diversified varietal landscape. Journal of Plant Pathology https://doi.org/10.1007/s42161-024-01653-9

Contact : frederic.suffert@inrae.fr