The effect of soil pH on the severity of Chocolate Spot infection on field bean varieties

Abstract

SummaryField bean varieties were grown for 2 years on five plots varying in pH from 4·7 to 8·4. Non-aggressive Chocolate Spot infection was shown to be greater on plants grown in soil of pH 4·7 and 5·8 than on those grown in soil of pH 6·7, 7·7 and 8·4. Seed weight per plant was greater on soil pH 7·7 than on soil pH 4·7, suggesting that acid soil reduced plant vigour and consequently increased disease susceptibility. Varietal differences in infection were shown, although absolute resistance was not observed. Varieties differed in their susceptibility on soils of varying pH, and also showed different stability for susceptibility over the varying environmental conditions.