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

Abstract

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. The clones displayed a range of maturity scores and it was demonstrated that these showed a relationship with the variation in observed disease symptoms. The deviation of symptom expression from a linear relation with maturity was taken to reflect a clone's actual resistance or susceptibility. The results showed agreement over years and it was suggested that such trials and methods of assessment might provide the basis for screening large numbers of clones.