Assessing varietal resistance to common scab in organic cereal production, particularly soft wheat

Common wheat smut (caused by the fungus Tilletia caries or Tilletia foetida) is a disease that is clearly on the rise in organic farming, threatening the stability of the French organic cereal sector. There is an urgent need to find control methods suitable for organic farming, given that no seed treatment is 100% effective. The use of varietal resistance appears to be a promising approach to limiting the spread of the disease. Since 2000, a trial designed to assess the resistance of soft wheat varieties to Tilletia caries has been conducted annually by ARVALIS-Institut du végétal. These trials have revealed significant variability in response to this pathogen amongst the varieties grown in France. However, no variety meeting the specific criteria for organic farming exhibits sufficient levels of resistance. At the same time, a European trial network has revealed a strong genotype × environment interaction, highlighting the need to consolidate these initial observations by increasing the number of trial sites, as well as to identify the virulence genes present in France and the resistance genes present in the varieties.