Response of Several Apple Varieties to Powdery Mildew (podosphaera Leucotricha) Attack in Central Transylvania Conditions

The response of apple cultivars to powdery mildew attack – Podosphaera leucotricha (Ell. et Everh.) Salm. – on leaves and shoots, for seven years (1990-1996), emphasised a large variability for this character existing within 75 apple varieties tested in an experimental field at the Fruit Research Station in Cluj-Napoca, Central Transylvania, Romania. The experimental results confirmed that the cultivars of the Jonathan group are highly susceptible to powdery mildew (e.g. Jonathan, Jonne Spur, Jonathan Smith, Black John, Jonathan Watson, Nüred Jonathan, Delia, Aromat de vară, Roşu de Cluj). Cultivars Gloster, Starkrimson and Prima were registered with a low attack degree. None of the tested cultivars were included in the category “No attack”. Out of all varieties, 21 of them representing 28.0% were registered with a very high attack, both on leaves and shoots.