Stomatal penetration: the cornerstone of plant resistance to the fungal pathogen Zymoseptoria tritici

Melissa Battache, Caroline Frey, Marta Suarez-Fernandez, Madison Van’t Klooster, Florence Cambon, Andrea Sanchez Vallet, Marc-Henri Lebrun, Thierry Langin, Cyrille Saintenac
Université Clermont Auvergne, INRAE, GDEC, Clermont-Ferrand, France

Septoria tritici blotch (STB), caused by the fungal pathogen Zymoseptoria tritici, is a significant threat to wheat production. STB management strategies primarily involve the use of fungicides and resistant cultivars. Breeding cultivars with more efficient resistance against this devastating disease requires understanding the diversity of plant resistance mechanisms. Various types of resistance against this pathogen have been identified, ranging from non-host resistance to major host resistance genes known as Stb. To date, 23 Stb genes have been mapped to the wheat genome, but the molecular and physiological mechanisms associated with resistance remain poorly understood. By using a combination of different phenotyping approaches and quantitative cytological analyses of Z. tritici infection, we identified a common pattern of Z. tritici growth inhibition associated with plant resistance. In all resistant grass plants, Z. tritici was stopped, at least partially, during stomatal penetration. The intensity of this early plant control process varied depending on resistance types, with quantitative resistances being the least effective. Furthermore, it was associated with stomatal closure in the case of the Stb16q resistance. These findings suggest the presence of a major common resistance mechanism involving stomata across the diverse types of resistance against Z. tritici.