Are Epiphytic Microbial Communities in the Carposphere of Ripening Grape Clusters (Vitis vinifera L.) Different between Conventional, Organic, and Biodynamic Grapes?
Elizabeth Kecskeméti, Beate Berkelmann-Löhnertz, Annette Reineke
Abstract
Using barcoded pyrosequencing fungal and bacterial communities associated with grape berry clusters (Vitis vinifera L.) obtained
from conventional, organic and biodynamic vineyard plots were investigated in two subsequent years at different stages during
berry ripening. The four most abundant operational taxonomic units (OTUs) based on fungal ITS data were Botrytis cinerea,
Cladosporium spp., Aureobasidium pullulans and Alternaria alternata which represented 57% and 47% of the total reads in 2010
and 2011, respectively. Members of the genera Sphingomonas, Gluconobacter, Pseudomonas, Erwinia, and Massilia constituted
67% of the total number of bacterial 16S DNA reads in 2010 samples and 78% in 2011 samples. Viticultural management system
had no significant effect on abundance of fungi or bacteria in both years and at all three sampling dates. Exceptions were A.
alternata and Pseudomonas spp. which were more abundant in the carposphere of conventional compared to biodynamic berries,
as well as Sphingomonas spp. which was significantly less abundant on conventional compared to organic berries at an early
ripening stage in 2011. In general, there were no significant differences in fungal and bacterial diversity indices or richness evident
between management systems. No distinct fungal or bacterial communities were associated with the different maturation stages or
management systems, respectively. An exception was the last stage of berry maturation in 2011, where the Simpson diversity index
was significantly higher for fungal communities on biodynamic compared to conventional grapes. Our study highlights the existence
of complex and dynamic microbial communities in the grape cluster carposphere including both phytopathogenic and potentially
antagonistic microorganisms that can have a significant impact on grape production. Such knowledge is particularly relevant for
development, selection and application of effective control measures against economically important pathogens present in the
grape carposphere.