THE INFLUENCE OF MG AND CA DEFICIENCY ON SUSCEPTIBILITY OF KOHLRABI TOWARDS BOTRYTIS-CINEREA INFECTION

The effect of Mg and/or Ca deficiency on susceptibility of leaves to fungal infection was investigated by Botrytis cinerea inoculation studies in kohlrabi plants (Brassica oleracea var. gongylodes) under controlled conditions. Plants were cultivated in sand and provided with nutrient solutions. During the experimental period of 6 weeks plants of the Mg and/or Ca deficiency treatments were supplied with a modified Hoagland solution containing only 15 % of the respective mineral elements of the control. The status of mineral elements and chlorophylls in the leaf material was determined by chemical analysis. Susceptibility to B. cinerea infections in the treatment groups varied with leaf age. In young, 3-week-old leaves an increased level of leaf lesions was detected in the Ca deficiency plants, in 6-week-old leaves a higher degree of infection was established in the Ca and Mg deficient plants 72 hrs. following inoculation with conidial solution. There was a strong relationship between tissue damage induced by fungal infection and selected parameters of chlorophyll fluorescence induction curves. The extend of leaf lesions also correlated with increased ethylene release as measured 72 hrs. after inoculation of plant material.