Potential of Trichoderma spp. for Biocontrol of Aflatoxin-Producing Aspergillus flavus

Abstract

The inhibitory action of 20 antagonistic Trichoderma isolates against the aflatoxigenic isolate A. flavus ITEM 9 (Af-9) and their efficacy in reducing aflatoxin formation in vitro were examined. Production of metabolites with inhibitory effect by the Trichoderma isolates was also investigated. Antagonistic effect against Af-9 was assessed by inhibition of radial growth of the colonies and by fungal interactions in dual confrontation tests. A total of 8 out of 20 isolates resulted in a significant growth inhibition of 3-day-old cultures of Af-9, ranging from 13% to 65%. A total of 14 isolates reduced significantly the aflatoxin B1 (AfB1) content of 15-day-old Af-9 cultures; 4 were ineffective, and 2 increased AfB1. Reduction of AfB1 content was up to 84.9% and 71.1% in 7- and 15-day-old cultures, respectively. Since the inhibition of Af-9 growth by metabolites of Trichoderma was not necessarily associated with inhibition of AfB1 production and vice versa, we investigated the mechanism of reduction of AfB1 content at the molecular level by examining two strains: one (T60) that reduced both growth and mycotoxin content; and the other (T44) that reduced mycotoxin content but not Af-9 growth. The expression analyses for the two regulatory genes aflR and aflS, and the structural genes aflA, aflD, aflO and aflQ of the aflatoxin biosynthesis cluster indicated that neither strain was able to downregulate the aflatoxin synthesis, leading to the conclusion that the AfB1 content reduction by these Trichoderma strains was based on other mechanisms, such as enzyme degradation or complexation. Although further studies are envisaged to identify the metabolites involved in the biocontrol of A. flavus and prevention of aflatoxin accumulation, as well as for assessment of the efficacy under controlled and field conditions, Trichoderma spp. qualify as promising agents and possible alternative options to other biocontrol agents already in use.

Characterization and mechanism of aflatoxin degradation by a novel strain of Trichoderma reesei CGMCC3.5218

“…A total of 65 Trichoderma isolates from different geographical origins, including China, Italy, the United States, Australia and Borneo, and different sources such as soil, fruit and wood were examined ( Supplementary Table S1 ). In contrast, the sequences of the internal transcribed spacer regions ITS-1 and ITS-2 of the nuclear rDNA are relatively stable, which represents a moderate amount of information and could be used to identify the isolates ( Fanelli et al, 2018 ; Ren et al, 2022 ). All the isolates were molecularly characterized by analysis of the sequences of the internal transcribed spacer regions ITS-1 and ITS-2 of the nuclear rDNA.…”

“…The aflatoxin determination was carried out according to Ren et al (2022) . Aflatoxins were analyzed by an HPLC-FLD apparatus of the series 1,100 from Agilent Technologies (Santa Clara, CA, United States), with a fluorescence detector and an HPLC C-18 column of 4.6-mm inner diameter, 250-mm length, and 5-μm particle size.…”

Recent Research on Fusarium Mycotoxins in Maize—A Review

“…Competition for nutrients or space, synthesis of volatile and non-volatile antibiotics and lytic enzymes, inactivation of pathogen enzymes, and parasitism are all direct consequences. Indirect impacts include morphological and metabolic changes in the host plants, such as stress tolerance, inorganic nutrient solubilization or sequestration, and induction of fungal phytopathogen-caused disease resistance [ 161 ].…”

Trichoderma Enzymes for Degradation of Aflatoxin B1 and Ochratoxin A

“…Trichoderma fungi suppress foliar and soil-borne plant pathogens; enhance plant resistance to diseases and abiotic stresses; and promote mineral nutrition, plant growth, and crop productivity [19,20]. These beneficial fungi are competitors in the soil environment to pathogen species and synthesize secondary metabolites to decrease plant pathogens [21] by an interference competition [22]. Moreover, Trichoderma fungi can produce peroxidases, glucanases, chitinases, and cellulases, enzymes active against phytopathogens [23,24] used in the postharvest disease management of papaya, apple, tomato, pear, mango, banana, potato, and berries [25][26][27][28][29][30][31][32][33][34][35][36][37].…”