Study of selected mechanisms of oat tolerance to cadmium and powdery mildew

This study evaluates the tolerance mechanisms of different varieties of oats (Avena sativa L., vars. Aragon, Bay Yan 2, Ivory, Racoon, and Vaclav) to cadmium (50 mg·kg⁻¹ soil applied on day 22, Cd treatment), the pathogen (Blumeria graminis f. sp. avenae, applied on day 35, P treatment), and their simultaneous effect (P + Cd treatment). Cd accumulation was generally higher in the infected plants (P + Cd) and depended on the genotype. The tested oat vars. were more sensitive to P than to Cd, which was reflected in a significant reduction (> 40%) in photosynthetic pigment content, an increase in polyphenol content, higher lipid peroxidation in membranes, and increased activity of total β-1,3-glucanase and catalase in infected leaves. A significant increase in calcium content was observed in the leaves of the P + Cd treatment. The reduced glutathione content in the Cd and P + Cd treatments (compared to the P treatment) in most of the tested vars. suggests different roles for glutathione in defence against Cd (metal sequestration) and P (antioxidant role). The reduction in lipid peroxidation, polyphenol content, and total β-1,3-glucanase activity in plants of the P + Cd treatment suggests a potential priming effect of cadmium on defence mechanisms. The obtained results have the potential to predict oat behaviour not only under cadmium stress or powdery mildew infection, but also under combined stress conditions.