Seleção de isolados de Bacillus spp. com potencial antagonista para controle de Fusarium oxysporum f. sp. cubense

Abstract

Banana farming is an activity of great economic importance throughout the world, with numerous producing countries. Brazil has a prominent role in it, occupying the fourth place in the production ranking. The Panama disease is endemic disease in banana producing areas, is one of the greatest problems for banana industry worldwide, some varieties showed to be extremely susceptible to the pathogen, impeding the economic exploitation of the banana crop in such region. Bacteria of the Bacillus genus are some of the most widely used and commercialized biological control agents in the world. These bacteria have several mechanisms of antagonism, such as metabolites production, enzymes, siderophores, volatile organic compounds and others, that ensure competitive success against other microorganisms. In this context, this study aimed to select species of the genus Bacillus, that present antagonistic potential against Panama disease. Therefore, 50 isolates of Bacillus spp. obtained from the banana and radish rhizosphere were submitted to in vitro tests against Fusarium oxysporum f. sp. cubense (FOC), causal agent of the Panama disease. In total, 23 isolates were capable to inhibit mycelial growth, reducing up to 61.95% of pathogen growth. It was also evaluated the production capacity of volatile compounds of the isolates that stood out the most in the antagonism test. Of the five isolates (44, 59, 71, 99 and 186) of Bacillus spp. tested in the test of volatile compounds, four (59, 71, 99 and 186) presented the best inhibitions of FOC mycelial growth when compared to the control. The isolates that stood out the most were submitted to tests of inhibition against multiple pathogens. Only the pathogens Rhizoctonia solani, causal agent of Rhizoctonia canker in melon, Lasiodiplodia theobromae, causal agent of gummosis in cashew tree and L. theobromae causal agent of stem-end rots in melon were not inhibited by the bacterial isolates. From this study, it can be concluded that the most promising isolates, considering the in vitro mechanisms of antagonism are the isolates 44, 59, 71, 99 and 186, especially the isolate 186 which showed a good activity in all tests conducted.