Prospecting for New Potential Biocontrol Agents Against Colletotrichum lindemuthianum, the Causal Agent of Bean Anthracnose

The repertoire of biological controllers for Colletotrichum lindemuthianum (Cl), the agent of anthracnose, remains limited. Aiming to expand this repertoire, eighteen cultivable bacteria isolated from soils and plants from the Iron Quadrangle were prospected as biocontrol agents of this fungus. Cl strain C89 (ClC89) was used as a model in direct (with the presence of antagonist) and indirect assays (with the presence of antagonist-secreted biomolecules). The best candidates for Cl inhibition were validated with the ability to produce inhibitory volatile compounds, secrete thermostable inhibitory molecules, solubilize inorganic phosphate and, produce siderophores and biofilm. These isolates are also evaluated for tolerating metals and metalloids (Mn, Fe, As, Pb, Cl, Cd and, Cu), resisting variations in UV-C, pH and oxidizing agents, and were identified by molecular analysis. Five isolates (C74, LR1, C23, RPT1, and RA4) presented high inhibition rates in the growth of the ClC89 (above 75%) either direct or indirect contact, with the RPT1 capable of secreting diffusible thermo-compounds. Identified as Pantoea (RPT1 and C23) and Acinetobacter (C74 and RA4) genera, these isolates showed high tolerance profiles to abiotic factors, which are critical in maintaining these organisms in the field. Although it presented significant potential for application, the molecular identification of the LR1 strain could not be precisely established. The five isolates proved to be promising biocontrol inoculants of C. lindemuthianum to be evaluated in the field and again highlight the potential of ecosystem services associated with microorganisms from a poorly studied geosystem, the Brazilian Iron Quadrangle. Graphical AbstractStages involved in the process of prospecting bacterial isolates for the control of Colletotrichum lindemuthianum