Characterization of microbial communities and fungal metabolites on field grown strawberries from organic and conventional production

Birgit Jensen, Inge M. B. Knudsen, Birgitte Andersen, Kristian Fog Nielsen, Ulf Thrane, Dan Funck Jensen, John Larsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The background levels of culturable indigenous microbial communities (microbiotas) on strawberries were examined in a field survey with four conventional and four organic growers with different production practise and geographic distribution. The microbiota on apparently healthy strawberries was complex including potential plant pathogens, opportunistic human pathogens, plant disease biocontrol agents and mycotoxin producers. The latter group was dominated by Penicillium spp. and Aspergillus niger was also isolated. As expected, bacteria were the most abundant and diverse group of the strawberry microbiota followed by yeasts and filamentous fungi. No obvious correlation between grower practice and the strawberry microbiota was observed. Differences between microbiotas on strawberries from conventional systems with up to 10 fungicide spray treatments and organic production systems were insignificant. Mycotoxins were not detected in mature strawberries from any of the eight different growers neither in additional samples of low quality berries. However, isolates of Penicillium expansum and A. niger produced high amounts of mycotoxins when incubated on strawberries at 25°C. Penicillium polonicum produced cyclopenol, cyclopenin, and viridicatin on the artificially infected berries, while Alternaria arborescens produced tenuazonic acid, Alternaria tenuissima produced altertoxin I and altenuene, and Trichoderma spp. produced several peptaibols. In conclusion, native strawberry microbiotas are highly diverse both in terms of taxonomic groups and functional traits that are important in relation to plant and human health.
    Original languageEnglish
    JournalInternational Journal of Food Microbiology
    Volume160
    Issue number3
    Pages (from-to)313-322
    ISSN0168-1605
    DOIs
    Publication statusPublished - 2013

    Keywords

    • Microbial communities
    • Strawberry phyllosphere
    • Biocontrol
    • Organic production
    • Secondary metabolites
    • Mycotoxins

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