Effect of pre-harvest application with some organic acids and plant oils on antioxidant properties and resistance to Botrytis cinerea in pepper fruits

•Pre-harvest application with salicylic and citric acids on antioxidant properties and resistance to Botrytis cinerea in pepper fruits.•Effect of pre-harvest application with clove and olive oils on antioxidant properties and resistance to Botrytis cinerea in pepper fruits.•Spraying pepper plants under plastic houses condition with salicylic, citric acids and clove or olive oils reduced development of grey mold on fruits during cold storage.•All tested plant oils and citric acid increased the epidermis and cuticle thickness and decreasing simultaneously the disease infection incited by Botrytis cinerea on pepper fruits.•The high antioxidant activities of clove treated pepper fruits were attributed to its high contents of total phenolic compounds. Pepper is planting widely in plastic houses and the fields; Botrytis cinerea infection starts in the field, but is strongly appear during storage. Results revealed that spraying pepper plants under plastic houses condition with salicylic, citric acids and clove or olive oils at different concentration (Salicylic acid at 8 mM and citric acid at 30 Mm, meanwhile clove and olive oils at rate 5 m/l) reduced development of grey mold on fruits during cold storage. The mycelial growth of B. cinerea was the most sensitive to salicylic acid, where it completely inhibited the growth of tested fungus at concentrations 4 and 8 Mm. Clove and olive oils at their tested concentrations (2.5 and 5 m/l) reduced the growth of Botrytis cinerea to 100%. All tested plant oils and citric acid increased the epidermis and cuticle thickness and decreasing simultaneously the disease infection incited by Botrytis cinerea on pepper fruits. Spraying pepper plants with all tested treatments increased peroxidase and polyphenoloxidase activities at 2 and 5 days from storage in naturally infected pepper fruits and at 5 days from storage in infected fruits with B. cinerea. The total phenolic compounds (TPC) and antioxidant activity (2,2-Diphenyl-1-picrylhydrazyl DPPH) were determined. Natural infection treated by clove 2.5 m/l had the highest content of TPC. The high antioxidant activities of clove treated pepper fruits were attributed to its high contents of total phenolic compounds.