Influence of nitrogen nutrition on powdery mildew (Sphaerotheca fuliginea) infection and metabolism of cucumber (Cucumis sativus)

Abstract

The relationship between N nutrition, plant metabolism and powdery mildew infection, an important disease in glasshouse cucumber production, was studied on plants grown in nutrient solution. Strong N deficiency did not restrain infection but instead restrained growth of the fungus after successful infection. This was presumably due to a shortage of some amino acids. NO3 excess diminished hyphae development. This was not caused by factors which are generally discussed in relation to powdery mildew development like carbohydrate content and activity of enzymes of phenol metabolism. Powdery mildew infection could not be reduced by controlled N nutrition without yield reduction.