Endophytic Trichoderma spp. for the control of common bean anthracnose
Authors:   , Alvarado Moreno Hanna Lorena 
Published: August 2023

Fungi of the Trichoderma genus can protect plants by mechanisms of action such as mycoparasitism, antibiosis, competition and/or systemic resistance induction. Isolates from megadiverse environments such as the Amazon rainforest may have the potential to protect plants of agronomic interest and provide information that amplify the current knowledge of the Trichoderma genus. The objective of the present work was to select Trichoderma spp. endophytes from the Amazon Forest with potential for use as biological control (BC) agents of common bean anthracnose caused by the phytopathogen Colletotrichum lindemuthianum and to know the mechanisms of action by which these selected isolates were able to protect the plants against the phytopathogen. First, 20 Trichoderma spp. isolates were evaluated in a greenhouse and four isolates were selected: Trichoderma sp. VIC44363 17F (T17F), Trichoderma sp. VIC44364 22F (T22F), Trichoderma koningiopsis 24F (Tk24F) and Trichoderma erinaceum 610F (Te610F) which also promoted the growth of common bean. The isolates T22F, Tk24F and Te610F were studied regarding the mechanism of action, whether it is mycoparasitism, antibiosis, competition and/or resistance induction. For this, it was evaluated whether the application site of the antagonist, before the application of the phytopathogen, would influence the BC efficiency. Isolates T22F, Tk24F and Te610F protected the plant when they were applied to the root and leaves in a preventive way, but the isolate Tk24F stood out because it protected the plant in a systemic way when it was applied only to the root and locally when it was applied in the aerial part; similarly, the isolate Te610F stood out because it had a local effect as the disease severity was reduced by application to the aerial part. Subsequently, with the in vitro experiments, it was determined that the isolates Tk24F and Te610F were the most efficient antagonists to C. lindemuthianum due to the mechanisms of mycoparasitism, antibiosis and competition. Finally, with the T17F isolate, a separate study was carried out due to the possibility of it producing mycotoxins that limit its use as a BC agent, as it belongs to the Brevicompactum clade, which is recognized for producing mycotoxins of the trichothecenes type. The characterization of the T17F isolate was carried out through in vitro experiments in which the mechanisms of mycoparasitism, antibiosis and competition were evaluated, and the genome was sequenced to perform a comparative analysis with genomes from other species belonging to the same clade. By in vitro test it was determined that antibiosis is the mechanism used by the T17F isolate to antagonize C. lindemuthianum and other phytopathogenic fungi. By comparing trichothecenes cluster of the isolate Trichoderma sp. VIC44363 with the cluster of T. brevicompactum and T. arundinaceum, it was concluded that Trichoderma sp. VIC44363 can produce the mycotoxin trichodermin, as it lacks the tri23 gene. Trichoderma sp. VIC44363 has the potential to produce new compounds, as it has a cluster that is different from those found in T. brevicompactum. Trichoderma erinaceum 610F and T. koningiopsis 24F are potential biocontrol agents for C. lindemuthianum, due to the joint use of mechanisms that inhibit the infection of C. lindemuthianum. Keywords: Endophytes. Transformation with RFP. Colonization. qPCR. Transcriptomics. Genomics. Brevicompactum. Viride.