Cereal disease

Context and objectives

Every year, wheat crops are subjected to intense parasitic pressures. These originate from a complex set of bio-aggressors, which attack wheat plants all along their developmental cycle, from seed to ear. The most damaging diseases of fungal origin (Septoria leaf blotch, Fusarium head blight and rust) are responsible for significant declines in annual yields and quality losses, and even sanitary issues. Within the framework of the agroecological transition, the mobilization of the natural plant immunity is and will be one of the best strategies to ensure, in association with innovative agronomic solutions, an effective control of pests and pathogens, while reducing our dependence towards conventional phytosanitary products.

In this context, the "Cereal Diseases" team develops projects focused on the determinism and functioning of wheat resistances against Septoria tritici blotch (STB) and Fusarium head blight (FHB). These two fungal diseases have very different biology, modes of infection and epidemiology. STB is a leaf disease, caused by the fungal specie Zymoseptoria tritici, whose large genetic diversity renewed every year (sexual reproduction) allows it to rapidly bypass the resistance genes deployed in  wheat varieties. FHB is a disease of spikes, caused by a complex of several species (>20 species belonging to the Fusarium genus and 2 species belonging to Microdochium genus). The main specie present in French and European fields is F. graminearum. While resistance to STB can be quantitative or qualitative, with >20 known major resistance genes (Stb genes), the sources of resistance to FHB are all quantitative (>650 known QTL identified in 22 different chromosomal regions). The MDC team has been involved for about ten years in the characterization of the biological processes underlying resistance versus susceptibility of wheat to these two diseases, through the cloning and functional analysis of resistance genes (R) and the functional characterization of effectors associated with the identification of their plant targets, the so-called susceptibility factors (S). More recently, the projects of the MDC team have been extended to study the impact of environmental factors, biotic or abiotic, on the efficiency and stability of resistance.

Recently, the MDC projects have taken a clear functional orientation, with in particular the study of the complex biological systems represented by plant/pathogen interactions, using approaches (data integration, gene networks, modeling) that are grouped under the term of Systems Biology. The ambition is to move towards a more predictive biology.

Research topics

The projects of the MDC team, structured around three complementary research axes, have a double objective: (1) to provide original information on the molecular and physiological mechanisms involved in the control and development of these two wheat diseases, and (2) to make new genes, new genetic combinations and original mechanisms available for breeding. This intends to broaden the spectra (STB) and the levels of resistance (STB, FHB), and to improve their durability.  

The challenge is to build sustainable resistances by diversifying the sources of resistances, improving the knowledge of their genetic, molecular and physiological bases and combining them with other strategies (Integrative Pest Management).

Genetic determinism and function of resistance to septoria

Leader C. Saintenac

• § Identification of new sources of resistance (accessions, major genes, QTLs)
• § Cloning and functional analysis of genes that confer resistance to STB (Stb genes)
• §  Molecular and physiological characterization of mechanisms mediated by Stb genes

Sensitivity factors, an alternative to the use of classical resistances

Leader L. Bonhomme

• § Integrative molecular physiology of the interaction between wheat and the mycotoxigenic fungus Fusarium graminearum
• § Identification of effectors and genomic determinants of F. graminearum aggressiveness and their targets in plant
• § Specificity of the molecular and physiological mechanisms of interaction: comparative analysis of Fusarium versus Microdochium

Impact of environmental factors on the plasticity/stability of resistances

Leader T. Langin

• § Analysis of the specific response of wheat to a combination of biotic x abiotic stress (high [CO₂]atm, drougth, ...)
• § Contribution of wheat-associated microbial communities (microbiota) to wheat resistance - Holobiont concept