Abstract
The transition from conventional to organic agriculture is often challenged by the adaptation of biological control agents to environments heavily exposed to agrochemical pollutants. We studied Trichoderma species isolated from living leaf tissues of wild Rubiacaeae (coffee family) plants to determine their fungicide tolerance and potential for bioremoval. First, we assessed the in vitro tolerance to fungicides of four Trichoderma isolates (Trichoderma rifaii T1, T. aff. crassum T2, T. aff. atroviride T3, and T. aff. strigosellum T4) by placing mycelial plugs onto solid media supplemented with seven different systemic and non-systemic fungicides. After a week, most of the fungicides did not significantly inhibit the growth of the isolates, except in the case of cyproconazole, where the only isolate able to grow was T1; however, the colony morphology was affected by the presence of fungicides. Second, biological removal potential was established for selected isolates. For this experiment, the isolates T1, T2, and T4 were independently inoculated into liquid media with the fungicides azoxystrobin, chlorothalonil, cyproconazole, and trifloxystrobin. After 14 days of incubation, a removal of up to 89% was achieved for chlorothalonil, 46.4% for cyproconazole, and 33.1% for trifloxystrobin using viable biomass. In the case of azoxystrobin, the highest removal (82.2%) occurred by adsorption to fungal biomass. Ecotoxicological tests in Daphnia magna revealed that T1 has the highest removal potential, achieving significant elimination of every fungicide, while simultaneously detoxifying the aqueous matrix (except in the case of cyproconazole). Isolate T4 also exhibited an intermediate efficiency, while isolate T2 was unable to detoxify the matrix in most cases. The removal and detoxification of cyproconazole failed with all the isolates. These findings suggest that endosphere of wild plants could be an attractive guild to find new Trichoderma species with promising bioremediation capabilities. In addition, the results demonstrate that attention should be placed when combining certain types of agrochemicals with antagonistic fungi in Integrated Pest and Disease Management strategies or when transitioning to organic agriculture.
Highlights
The rapidly growing demand for food has put high pressure on the environment through the abuse of pesticides, especially fungicides (Duhamel and Vandenkoornhuyse, 2013)
Our results indicate a high activity in chlorothalonil biodegradation by the selected Trichoderma isolates
Endophytic Trichoderma isolates were able to tolerate and prevail under the presence of fungicides, generating more questions related to the mechanisms and effects of agrochemicals for the microorganisms living in agroecosystems
Summary
The rapidly growing demand for food has put high pressure on the environment through the abuse of pesticides, especially fungicides (Duhamel and Vandenkoornhuyse, 2013). This affects production costs of important crops around the world and threatens the livelihoods of millions of people (Jaramillo et al, 2011; Caffarra et al, 2012; Ramirez-Villegas et al, 2012). Coffee (Coffea arabica) is currently under great stress because its productivity and quality are affected by pathogenic fungi, causing enormous economic losses. Because the quality of coffee is correlated to adequate management against pathogens, safer environmental practices could help improve coffee cup quality (Feria-Morales, 2002). Sustainable and environmentally friendly disease management strategies, such as biological control, are urgently needed (Ayalew, 2014; Rice, 2018)
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