The relation of soluble manganese to the incidence of common scab in potatoes

The modifications of cell wall composition and water status of cucumber leaves induced by powdery mildew and manganese nutrition

Powdery mildew caused by Podosphaera fuliginea, is one of the most important diseases, damaging cucumber's yield worldwide. Among the different controlling ways, management of plant nutrition is an effective method. The present experiment was aimed to study the effects of foliar application of manganese (Mn) on disease suppression and to elucidate the possible mechanisms by which Mn-treated plants resist to fungal disease. Cucumber plants were hydroponically grown and sprayed by MnSO₄ alone and in combination with lysine (Lys) and methionine (Met) four days before pathogen inoculation. The results showed that the foliar application of Mn reduced the fungal disease severity by increasing of lignin, cellulose and pectin contents of cell wall (CW) and improving of leaf water status. The reduction of disease severity by application of MnSO₄, Mn + Lys and Mn + Met, were 40, 33, and 40% compared to control, respectively. The increases of lignin contents at the same treatments were 33, 27, and 36%, respectively. The leaf water potential (LWP) enhanced by foliar spray of above-mentioned fertilizers up to 15, 18, and 17%, respectively. The results of present study revealed that the Mn nutrition could control the cucumber powdery mildew by reinforcing of CW structure and reducing of water loss from infected leaves. The current findings are the first reports elucidating the CW-related defense mechanisms in which Mn has important role. The obtained results have a practical importance either in studies of plant physiology and biochemistry or in agricultural sciences for cost-effective control of powdery mildew in cucumber plants.