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Doctoral thesis, 2013

Phyllosphere of organically grown strawberries

Sylla, Justine


The use of biological control agents (BCAs) is regarded as a promising measure to control important foliar strawberry diseases such as grey mould (Botrytis cinerea) and powdery mildew (Podosphaera aphanis) in the organic strawberry cultivation. However, the use of biological control agents (BCAs) in the phyllosphere is still challenging as this environment is very harsh and dynamic, in particular under field conditions. In this thesis, the simultaneous use of BCAs was studied for its potential to overcome the challenges biological control in the phyllosphere imposes and, thereby, to achieve more consistent efficacies against B. cinerea and P. aphanis. In vitro tests revealed that inhibitory interactions can basically occur between two BCAs and that these are affected by nutritional factors. Leaf disc assays demonstrated that the simultaneous use of BCAs can result in improved suppression of P. aphanis, depending on the BCA constituents. Furthermore, several BCAs were applied as single or multiple strain treatments against B. cinerea in three years of field experiment and microbial interactions in the phyllosphere were investigated within these experiments. The simultaneous use of BCAs did not result in consistent B. cinerea control under field conditions. In the field experiment 2010, none of the tested single or multiple BCA treatments reduced B. cinerea. In the field experiments 2011 and 2012 B. cinerea incidence was significantly suppressed by simultaneously applied BCAs as opposed to single BCA treatments. Efficient BCA treatments, however, differed in 2011 and 2012. Microbial analyses on leaves from field grown strawberries by means of plate counts and 454 pyrosequencing revealed that the culturable and the non-culturable resident leaf microbiota considerably varied between different years of experiment but also in dependence on the strawberry's development stage. Likewise, the interactions between the resident microbial communities and introduced BCAs varied as well, which have shown to be associated with inconsistent efficacies of the tested BCAs in 2011 and 2012. Also, microbial investigations revealed shifts in fungal communities after introducing fungal BCAs, which however can be regarded as neglible due to the overall considerable dynamics of the phyllosphere microbiota.


microbial communities; phyllosphere; biocontrol; strawberry

Published in

Acta Universitatis Agriculturae Sueciae
2013, number: 2013:85
ISBN: 978-91-576-7908-6, eISBN: 978-91-576-7909-3
Publisher: Department of Biosystems and Technology, Swedish University of Agricultural Sciences

Authors' information

Sylla, Justine
Swedish University of Agricultural Sciences, Department of Biosystems and Technology (VH), general

UKÄ Subject classification

Agricultural Science
Environmental Sciences related to Agriculture and Land-use

URI (permanent link to this page)