Genes involved in resistance to powdery mildew in barley differentially modulate root colonization by the mycorrhizal fungus Glomus mosseae

Arbuscular mycorrhizal fungi (AMF) and Erysiphe graminis are obligate biotr ophic fungi with different outcomes in their interaction with plants, diffe rent targeted host tissues, but similar patterns of development and infecti on processes. These similarities raise the question of whether the two type s of biotrophic fungal infections have common features in their regulation. To investigate this question, we compared a number of Ror and Rar barley m utants susceptible to E.graminis f. sp. hordei, as well as their resistant progenitors, for susceptibility to infection by the AMF Glomus mosseae. The two powdery mildew-resistant lines BC Ingrid and Sultan presented a simila r reduction in G. mosseae development within roots when compared to the wil dtype cultivar Ingrid, indicating a systemic effect of the altered genes in the plant. Ror and Rar mutants, in which susceptibility to powdery mildew is restored, showed increased resistance to AM fungal development in their roots when compared to their progenitors, which suggests that corresponding mutations must have affected genes which differentially modulate symbiotic and pathogenic biotrophic plant-fungus interactions.