Figure 2

Thin-sections of healthy and infected sugar beet leaves stained with toluidine blue: healthy leaf with intact leaf structure, chloroplasts (chl) are located peripherally in the cells. Leaf infected with Cercospora beticola.at the border of tissue without macroscopic symptoms (marked with arrows) to symptomatic necrotic tissue (marked with asterisks) in the centre (c) of a mature symptom. Erysiphe betae infected leaf with mycelium (my) and conidia (co) on the upper leaf surface. The fungus has penetrated the epidermal cell wall, appressoria (a) and haustoria (h) were formed. Leaf with a ruptured pustule of Uromyces betae. The upper epidermis (ue) is detached from parenchyma, urediniospores (us) were released, and intercellular hyphae (ih) appear in the intercellular space of the mesophyll.