Abstract: In two experiments young cabbage plants in the 4/6-leaf-stage were supplied about eight weeks with nutrient solutions without nitrogen(oN),phosphorus(oP),calcium(oCa),and potassium(oK) in order to investigate the impact of deficiency of essential major elements on the pathogenesis of black spot disease caused by Alternaria brassicicola.Intact(Int) and detached(Seg) segments from one of the fully expanded leaves were used for inoculation.Lesion size was the parameter of the pathogenic activity.In experiment 1 deficiency nutrient solutions oN,oP and oCa were tested simultaneously in four replications.Supplying plants with the control solution(ck) that contained all mineral elements essential for plant growth caused the largest leaf spots whereas all other forms of host nutrition retarded the development of lesions significantly in the Int as well as Seg trials ranging oN oCa oP.In experiment 2 the nutrient solution oK was supplied and lesions were determined at 5,7 and 22 d.At the fifth day after inoculation differences between the various nutrition forms were significant.In comparison to the control series ckInt and ckSeg,the oK solutions restricted the progress in lesion size about 53% respectively 14%,whereas on the oKSeg series the spots were remarkable larger(37%) compared with the oKInt series.Lesion sizes increased with time,but at 22 d differences between the various forms of nutrition in both Int and Seg tissue became near identical.Correlation analysis showed that there was no significant association between symptom expression caused by different nutrition in intact and senescing host tissue,but when the data of all treatment series,including the 22 d group in the second trial,were involved,a correlation coefficient of r=0.61^* could be calculated,indicating a relatively close association in affecting symptom expression between living and rapidly senescing host tissue.

Key words: Cabbage, Alternaria brassicicola, Nutrient solution, Symptom expression

CLC Number: 

• S635.1