Andersen, Birgitte

Jensen, Birgit

Jensen, Dan Funck

Knudsen, Inge M. B.

Larsen, John

Nielsen, Kristian Fog

Thrane, Ulf

The main objectives of the this project were to examine the abundance ofapplied microbial pest control agents (MPCAs) and their metabolitescompared to that of the natural microbiota and to examine the compatibilitybetween MPCAs and conventional fungicides and their combination effects indisease control.A series of laboratory, growth chamber, semi-field and field experiments usingstrawberry as a model plant focusing on commercial microbial pest controlproducts (MPCPs) or laboratory MPCAs expected to be on the market within10 years served as our experimental platform.Initially the background level of indigenous microbial communities and theirmycotoxins/metabolites on strawberries was examined in a field survey with 4conventional and 4 organic growers with different production practise andgeographic distribution. Culturable bacteria, yeasts and filamentous fungiwere isolated and identified using both chemotaxonomy (fatty acids andmetabolite profiling) and morphological characteristics.Microbial communities on strawberries were complex including potentialplant pathogens, opportunistic human pathogens, plant disease biocontrolagents and mycotoxin producers. Bacteria were the most abundant anddiverse group of strawberry microbiota followed by yeasts and filamentousfungi. Grower practice did not seem to correlate with the strawberrymicrobiota. Limited difference between microbial communities onstrawberries from conventional and organic production systems was observed.Mycotoxins were not detected in strawberries from any of the 8 differentgrowers covering both fresh and worst-case (semi-rotted) berries. However,filamentous fungi from the genera Penicillium and Aspergillus isolated from thefield survey produced high amounts of carcinogenic mycotoxins when appliedto strawberries in vitro.A broad range of microbial biocontrol agents (MPCAs) including thecommercial Trichoderma based products TRI003, Binab-T and Supresivit andthe laboratory MPCAs Clonostachys rosea and Ulocladium atrum wereexamined concerning their target and non-target effects, production ofmycotoxins, fungicide sensitivity and performance (establishment, growth andsurvival).Among the MPCAs tested only the laboratory MPCAs C. rosea and U. atrumdemonstrated biocontrol effects against the strawberry pathogen Botrytiscinerea and the background microbial community was unaffected by both C.rosea and U. atrum.None of the fungal MPCAs produced any mycotoxins when applied toflowers in semi-field and field experiments, but strawberries artificiallyinoculated with Trichoderma-based MPCPs in vitro contained biologicallyactive fungal metabolites of the peptaibol family.8In general, fungicides employed in conventional strawberry production hadno fungicidal effects on any of the MPCAs. Establishment of Trichoderma(TRI003) on berries following flower application was poor and applyingfungicides prior to the MPCA application did not result in improved MPCAperformance.In conclusion, the relative importance of deliberately released fungal MPCAsand their metabolites in relation to that of the natural strawberry microbiotaseem to be limited when considering the potential risk from the naturalmicrobiota including mycotoxin producers and opportunistic humanpathogens. In addition, our results suggest that it is possible to combineMPCAs and fungicides in an integrated strategy, potentially reducing thelevels of fungicide applications

Online Research Database In Technology

Importance of microbial pest control agents and their metabolites In relation to the natural microbiota on strawberry.

Knudsen, Inge-Marie Birkedal

Copenhagen University Research Information System

Importance of microbial pest control agents and their metabolites in relation to the natural microbiota on strawberry

http://orbit.dtu.dk/ws/files/104322086/rm5179.pdf

Importance of microbial pest control agents and their metabolites In relation to the natural microbiota on strawberry.

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Online Research Database In Technology

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Copenhagen University Research Information System