Assessing varietal resistances to control common wheat bunt under organic cereal production and soft wheat, in particular

Common wheat bunt (caused by the fungus Tilletia caries or Tilletia foetida) is a disease whose incidence is clearly on the rise in organic farming, jeopardising the balance of the French organic cereal sector. Control methods adapted to organic farming must be found, especially since we know that no seed treatment is 100% effective. The use of varietal resistance appears particularly promising for limiting the spread of the disease. Since 2000, an experiment whose purpose is to assess the resistance of soft wheat varieties to Tilletia caries is conducted each year by the French plant institute, ARVALIS. These experiments make it possible to identify the existence of a wide behavioural variability with respect to this pathogen among the different varieties grown in France. However, no variety corresponding to the specific criteria imposed by organic agriculture has yet to show adequate levels of resistance. At the same time, a European testing network revealed a strong genotype X environment interaction, emphasizing the necessity of consolidating these initial observations by increasing the number of test sites and by identifying virulence genes present in France as well as resistance genes present in the different varieties.