Control of Botrytis cinerea by the resistance inducers benzothiadiazole (BTH) and hydrogen peroxide on white pepper fruits under postharvest storage

Pepper fruits were sprayed with benzothiadiazole (BTH) and hydrogen peroxide (H 2 O 2) three times after harvest. Three days after the third spray, pepper fruits were inoculated with Botrytis cinerea (10 5 conidia/ml under 20 °C, 99% relative humidity). Under postharvest conditions (without artificial inoculation) BTH at 0.9 mM and H 2 O 2 at 20 or 50 mM reduced the weight loss, natural rot rate and nitrate content, however, ascorbic acid content and the shelf-life of fruits were increased significantly.When pepper fruits were inoculated with the fungus and treated with BTH (0.9 mM) and H 2 O 2 (50 mM) treatments, disease severity was reduced to 29.6 and 34%, respectively, as compared with the control (77.3%). Diameter of necrotic lesions were 1.2 and 1.38 mm, respectively, as compared with the control (2.8 mm).BTH (0.9 mM) and H 2 O 2 (50 mM) increased the level of endogenous H 2 O 2 and total phenolic contents 3–6 days after inoculation (dai) which are considered to play a pivotal role in plant disease resistance. Activities of the antioxidant enzymes dehydroascorbate reductase (DHAR), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) decreased at 3 and 6 dai then increased between 9–15 dai. The effectiveness of BTH treatment was always higher than that of 50 mM H 2 O 2 (high concentration).Low concentration of H 2 O 2 (20 mM) enhanced the antioxidant activities in infected fruits, however, the level of H 2 O 2 and total phenolic compound contents were not altered significantly, thus, the fungus was not inhibited.The results showed that BTH (0.9 mM) and H 2 O 2 (50 mM) treatments enhanced disease resistance against the fungus early after inoculation by elevating the level of endogenous H 2 O 2 and phenolic contents. Low concentration of H 2 O 2 (20 mM) was able to increase activity of antioxidants which may contribute to symptom’s resistance but did not inhibit the pathogen importantly. It would seem that BTH and H 2 O 2 could be suitable to control postharvest diseases.