title: Characterization of microbial communities and fungal metabolites on field grown strawberries from organic and conventional production.
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.
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark. bje@life.ku.dk
authors.forename: Birgit
authors.initials: B
authors.lastname: Jensen
authors.forename: Inge M B
authors.initials: IM
authors.lastname: Knudsen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Andersen
authors.forename: Kristian Fog
authors.initials: KF
authors.lastname: Nielsen
authors.forename: Ulf
authors.initials: U
authors.lastname: Thrane
authors.forename: Dan Funck
authors.initials: DF
authors.lastname: Jensen
authors.forename: John
authors.initials: J
authors.lastname: Larsen
mesh_terms: D000383:Agriculture / Q000592:standards*; D001419:Bacteria / Q000737:chemistry / Q000302:isolation & purification; D058491:Bacterial Load; D018407:Bacterial Physiological Phenomena; D015169:Colony Count, Microbial; D005516:Food Microbiology; D058870:Food, Organic / Q000382:microbiology*; D031985:Fragaria / Q000737:chemistry* / Q000382:microbiology*; D005658:Fungi / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D009183:Mycotoxins / Q000032:analysis; D058871:Organic Agriculture
chemical_list: D009183:Mycotoxins