Epidemiologia da podridão negra do abacaxi e efeito de extratos vegetais no manejo da doença

Abstract

The black rot of pineapple fruit (Chalara paradoxa), is considered the main postharvest disease in the world. In this work we analyzed the influence of the inoculation method (disc and suspension), temperature (10, 15, 20, 25, 30 and 35 ºC), period of exposure to humidity (0, 6, 12, 24, 36 hours), and of the inoculums concentration (10, 102, 103, 104, 105, 106 and 107 conidia/mL) of three isolates of C. paradoxa (CFM-1183, CFM-1188 and CFM-1029) on the severity of the disease. It was also evaluated the effect of plant extracts in terms of physical and chemical changes. Three treatments were applied (plant extracts, Ecolife® and a fungicide) in concentrations of 25% (D1), 50% (D2), 75% (D3) and 100% (D4) for the plant extracts and 50, 100, 150, 200, 300 μL.mL-1 for the Ecolife® (citric extract) and a fungicide. Healthy pineapples were disinfected and immersed in a solution of the different treatments for five minutes. After 24 hours, inoculation with wounding on pineapple fruit with suspension of C. paradoxa in the concentration of 106 conidia/mL. After inoculation, fruits were kept in a moist chamber for 24 h. The severity was evaluated 5 days after inoculation. The diameter of the lesion in two diametrically opposite directions was measured. For the physiochemical factors of the treated fruits, it was evaluated tenors of vitamin C (mg of ascorbic acid.100 mg-1), titratable acidity(ATT), total soluble sugars (SST) and pH. Before the results obtained all isolates were found to be pathogenic. No significant differences in the method of inoculation and area of inoculation of the pineapple (stalk and equatorial), inoculated with wounds were observed. There was a significant influence of the inoculums concentration of C. paradoxa in the severity of the disease, being larger in the concentrations 106 and 107 conidia /mL. The establishment of the disease, may occur under 25 °C and 24 h of humidity period. All tested extracts showed fungitoxic properties. The treatments caused no significant changes in levels of TSS and TTA. There was a significant reduction in levels of vitamin C and pH compared to the control but remained within an acceptable for commercialization.