Responses of calcium-supplied Murcott IAC 221 tangor plants to Alternaria alternata infection

Abstract Alternaria brown spot - ABS (Alternaria alternata) causes lesions on fruits, leaves and branches of mandarins. The cost fungicide application is high alternative managements for the control need to be studied. We aimed evaluate calcium (Ca) nutrition mitigate effects ABS. Murcott IAC 221 tangor plants were nourished with nitrate at three different concentrations (30, 150 300 mg Ca L-1), N content was standardized in nutrient solution treatments (245 L-1 N) ammonium nitrate. In vitro vivo tests installed, evaluating severity area under disease progress curve (AUDPC), total proteins, peroxidase (POX), catalase (CAT), superoxide dismutase (SOD) hydrogen peroxide (H2O2), during four times. all evaluations a negative correlation observed between leaf AUDPC On other hand, there positive occurrence disease. treatment lowest concentration accumulation H2O2 hypersensitivity reaction (HR), low detoxification by CAT. There potential use supply as an management against fungus A. alternata.