CHEMICALLY-INDUCED RESISTANCE IN GREEN BEAN AGAINST BACTERIAL AND FUNGAL PATHOGENS

With the help of the chemical agent benzo [1,2,3] thiadiazole-7-carbot hioic acid-S-methyl ester (BTH), the active ingredient of the plant ac tivator Bion(R), induction of systemic acquired resistance (SAR) was a chieved in green bean (Phaseolus vulgaris cv. 'Dufrix') against differ ent fungi and one bacterial pathogen of agricultural importance. To in duce SAR, bean leaves were either sprayed directly with BTH or as a ne w developed form of application, bean seeds were allowed to germinate in the inducer solution. A minimal period of 4 days was necessary to o btain resistance against the biotrophic rust fungus Uromyces appendicu latus, the perthotrophic soil-borne pathogen Rhizoctonia solani, the c ausal agent of anthracnose Colletotrichum lindemuthianum and bacterial common blight caused by Xanthomonas campestris pv. phaseoli. No induc tion of resistance was found against bacterial halo blight caused by P seudomonas syringae pv. phaseolicola. In chemically activated plants, enhanced activities of the defence-related enzymes chitinase, beta-(1, 3)-glucanase and peroxidase were detected which are well known biochem ical markers for SAR.