Histological reactions of wheat resistant or sensitive against infection of Pseudocercosporella herpotrichoides
The microscopic observations reveal important histological differences between the sensitive or resistant varieties. The disease rapidly affect the whole of the first three leafsheath tissues in the “Étoile de Choisy” variety; in the “Roazon” variety, it only affects the first two sheaths. The inter‐ or intracellular mycelia can be observed both under the form of filaments more or less dilated or under the form of dense segments in the sensitive variety. However in the resistant variety, only short segments can be observed. The tissues of those two varieties are gradually destroyed when they are in contact with P. herpotrichoides hyphae, whereas the hyphae remain undamaged. In “Etoile de Choisy” the hyphae develop in great quantity whereas in “Roazon”, the development remains limited. In the variety Ae. ventricosa no. 11, which is very resistant, the parasite rarely penetrates into the more external cell layers of the first leaf sheath,‘those invaded host cells are destroyed by the mycelium but, at the same time, the mycelian hyphae degenerate and dilate. Thus, the Ae. ventricosa no. 11 tissues seem to be the seat of a strong fungic toxic reaction.