ABSTRACT
Of the postharvest banana diseases, anthracnose (Colletotrichum musae), stands out among the most important limiting factors in the world. In order to control this pathogen, we evaluated the fungitoxic activity of extracts and essential oils from Lippia sidoides Cham., Caryophillus aromaticus L. Hook and Eucalyptus citriodora; antagonists Trichoderma sp yeast IA8, and one isolate of Bacillus subtilis; resistance of the inductors Acibenzolar-S-Methyl, salicylic acid and phosphite; and antimicrobial products of sodium hypochlorite, chlorine dioxide, and potassium sorbate, both in vitro and in vivo. In vitro tests were incorporated into treatments through BDA + tetracycline culture (50 μg.mL -1) at concentrations of 5, 10, 15, 20, 25, 30 % (p/v) of each crude extract; 0, 25, 50 and 100 µL of each oil; 0.05g, 0.3g and 300 µL of the inductors Acibenzolar-S-Methyl, salicylic acid and phosphite respectively; and 0.1g, 25mL and 100µL of the antimicrobials potassium sorbate, sodium hypochlorite and chlorine dioxide, respectively. The antagonistic activity was determined by the method of paired cultures for Trichoderma sp. and by the funnel method for IA8 yeast, both cultured in Petri dishes containing BDA medium. B. subtilis (already drawn) was tested at the proportion of 100 μL/100 mL of BDA. Plates containing only BDA and the fungicide carbendazim (10 μL/100 mL) were used for comparative purposes. All treatments were distributed in a completely randomized design with five replicates each, and incubated at 28 ± 2°C in a 12 h photoperiod for seven days. Means were compared by Tukey test at 5 % probability. In vivo tests utilized “Silver” bananas with two holes each, into which were deposited 20 µL of each treatment used in vitro (extracts and essential oils, antagonists, sanitizer products and resistance inducers). Twelve hours after incubation, the bananas were inoculated with 20 µL of spore suspension of C. musae (2.7 x 104 conidia/ml) and distributed into plastic trays (5 bananas / bin / treatment), in a completely randomized design with each hole representing a repetition. Data were subjected to analysis of variance and means were compared by Tukey test at 5 % probability. The in vitro results demonstrated that the essential oils and extracts of L. sidoides and C. aromaticus at all concentrations tested, as well as salicylic acid and sodium hypochlorite, were as effective as the chemical control at inhibiting the pathogen growth at 100 %. The phosphite and antagonists Trichoderma sp. and B. subtilis also exerted great fungitoxicity with respective reductions of 91.8, 84.0 and 74.0 %. In vivo tests only Trichoderma sp and sodium hypochlorite showed significant reductions (over 50 %) in lesion development in bananas.
Keywords
Colletotrichum musae; fungitoxic activity; antagonism; post-harvest
