Screening for field resistance to early blight (Alternaria solani) in potatoes

27 clones were trialled in the Negev, Israel, in the Spring and Autumn seasons of 1984 and 1985, in a control area (kept disease free) and an Alternaria area (artificially infected withA. solani). Disease symptoms and maturities were assessed. Significant variation in symptom expression was detected between clones and seasons, as well as a significant interaction of clones by years by seasons. The symptoms showed low correlations between seasons but were larger between years within the same season.