Manifestation of black spot disease (Alternaria brassicicola) in intact leaves and detached leaf segments of cabbage plants grown in nutrient solutions without N, P, K and Ca

Abstract

In two experiments young cabbage plants in the 4/6-leaf stage were supplied for eight weeks with nutrient solutions without nitrogen (oN), phosphorus (oP), calcium (oCa) or potassium (oK) in order to investigate the impact of withholding essential major elements on the development of black spot disease (Alternaria brassicicola) in intact leaves (variant Int) and detached leaf segments (variant Seg). A complete solution (Co) that contained all mineral elements essential for the growth of the host plant served as control. Lesion size in millimetres was measured as parameter of the pathogen activity. In the first trial, solutions oN, oP, oCa, and Co were tested simultaneously in four replications. Lesion size was estimated 5 days after inoculation (dai). In the second trial, only the solutions oK and Co were supplied in one replication and lesions were determined at 5 and 22 dai.