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Leaf Microbiota of Strawberries as Affected by Biological Control Agents

October 2013 , Volume 103 , Number  10
Pages  1,001 - 1,011

Justine Sylla, Beatrix W. Alsanius, Erika Krüger, Annette Reineke, Stephan Strohmeier, and Walter Wohanka

First, third, fourth, and sixth authors: Geisenheim University, Von-Lade-Str. 1, DE-65366 Geisenheim, Germany; first and second authors: Swedish University of Agricultural Sciences, Department of Biosystems and Technology, P.O. Box 103, SE-23053 Alnarp, Sweden; and fifth author: FreshX Consulting & Development, Walldorferstraße 26, DE-69226 Nußloch, Germany.

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Accepted for publication 13 May 2013.

The increasing use of biological control agents (BCAs) against Botrytis cinerea in strawberry raises the question of whether there are any undesirable impacts of foliar applications of BCAs on nontarget microorganisms in the phyllosphere. Therefore, our objective was to investigate this issue within a field study. Strawberry plants were repeatedly sprayed with three BCAs—namely, RhizoVital 42 fl. (Bacillus amyloliquefaciens FZB42), Trianum-P (Trichoderma harzianum T22), and Naturalis (Beauveria bassiana ATCC 74040)—to suppress Botrytis cinerea infections. Microbial communities of differentially treated leaves were analyzed using plate counts and pyrosequencing and compared with the microbial community of nontreated leaves. Plate count results indicate that the applied Bacillus and Trichoderma spp. survived in the strawberry phyllosphere throughout the strawberry season. However, no significant impacts on the leaf microbiota could be detected by this culture-dependent technique. Pyrosequencing of internal transcribed spacer ribosomal RNA and 16S RNA sequences revealed a change in fungal composition and diversity at class level after the introduction of T. harzianum T22 to the phyllosphere, whereas the bacterial composition and diversity was not affected by either this Trichoderma preparation or the other two BCAs. Our results suggest that pyrosequencing represents a useful method for studying microbial interactions in the phyllosphere.

© 2013 The American Phytopathological Society