Alternatives in the control of Alternaria brown spot in ‘Dancy’

ABSTRACT The tangerine ‘Dancy’ has desirable characteristics such as color, aroma, flavor and wide acceptance by the market. This variety is highly produced in the state of Paraíba but is susceptible to Alternaria brown spot (MMA), caused by Alternaria alternata, responsible for compromising the fruit quality in tangerine producing regions. To prevent this disease, research using alternative products has been expanded. Therefore, the objective of this study was to determine the potential of the extract of Caesalpinia ferrea and Chitosan® in the management of MMA in fruits of ‘Dancy’ tangerine. The fruits were disinfested and immersed in extract of C. ferrea at concentrations of 0, 10, 100, 500 and 1000 µg/mL, and Chitosan® at 0.5, 1.0, 1.5 and 2.0 g/L. After 24 h of the application of products, the fungus A. alternata was inoculated (105 spores/mL). From the second day after inoculation (DAI), severity (AUDPC) was daily evaluated. For analysis of the activities of phenylalanine ammonia-lyase, peroxidase and polyphenol oxidase, three fruits/replicate were taken on the first and twelfth days of the experiment. The design was completely randomized including 9 treatments (concentrations of products) and 5 replicates with 5 fruits, which constituted an experimental unit with 225 fruits. Regression analysis and Dunnett’s test (P ≤ 0.05) were performed by using SAS® System 9.3 software. The concentrations of 500 µg/mL of C. ferrea extract and 1.5 g/L Chitosan® reduced the severity of Alternaria brown spot and promoted high activities of the enzymes in ‘Dancy’ tangerine fruits.