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Endophytic bacteria as biocontrol agents of Moniliophthora roreri, a cacao (Theobroma cacao) pathogen

Pedro Jiménez: Universidad Militar Nueva Granada

<div><em>Moniliophthora roreri</em>, the causal agent of frosty pod rot, is a great constraint for cacao (<em>Theobroma cacao</em>) production in Colombia. Since efforts to control this fungus have high environmental costs, alternatives such as the use of microorganisms in biological control schemes are needed. Therefore, this study aimed to assess the potential of cacao endophytic bacteria as biocontrol agents of this fungus. Endophytes were isolated from healthy cacao leaves at three farms in Cundinamarca, Colombia. A leaf was collected at each of three different positions on the trees (apical, medium high, and stem base), and all endophytes from each leaf were recovered. A total of 142 endophytic bacteria were isolated, screened <em>in vitro</em> for antagonism against <em>M. roreri,</em> and identified molecularly using the 16S rRNA region. Also, 2058 fungi were isolated, and fungal colonization increased with the leaf age (lower leaves rendered 54% of the isolated fungi). Contrary to fungi, apical leaves rendered the highest amount of bacterial isolates (44% of the total). Out of the 142 bacteria tested, 83 showed antagonism activity against <em>M. roreri,</em> with colonial growth inhibition greater than 60%. Those bacteria isolated from apical leaves produced the largest pathogen growth inhibition. The results of this study indicate that the community of endophytes changed with leaf age, and that most of the bacterial endophytes of cacao have biocontrol potential activity against <em>M. roreri</em>. Financed by Universidad Militar Nueva Granada Project: CIAS-2301.</div>