Benzothiadiazole (BTH)-induced resistance

Abstract Greenhouse-cultivated tomato, bean and cucum- ber suffer great economic losses due to grey mould, caused by Botrytis cinerea. Benzothiadiazole (BTH) is a chemical analogue of salicylic acid that induces resistance in a variety of plants by activating the systemic acquired resistance (SAR) pathway. Here, we investigated the effects of foliar applications of different concentrations of BTH on resis- tance to B. cinerea in these plants and on plant vegetative and generative growth. Leaf treatments with 1 up to 50 mg/l BTH resulted in increased protection of tomato against B. cinerea. However, on bean and cucumber, only concentra- tions of 250 mg/l and higher, strongly reduced susceptibility against B. cinerea. Moreover, BTH concentrations above 100 mg/l had a significant negative effect on plant height, flower and fruit numbers in bean and cucumber plants under pathogen-free conditions, whereas in tomato only the highest BTH dose (1000 mg/l) resulted in a significant negative effect on vegetative and generative growth. We hypothesize that the protective effects observed on bean and cucumber plants treated with higher levels of BTH are due to a general stress response, which is distinctly different from the BTH-inducedresistance observed in tomato at lower concentrations of the compound without negative effects on plant growth.

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