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.
Highlights
Grapevines, cultured on approximately 7.5 million ha in vineyards throughout temperate regions worldwide [1], are hosts for complex communities of microorganisms and arthropods, which can significantly influence both the quantity of the yield as well as the quality of must and wine [2, 3]
From the total number of reads in 2010, 17,937 operational taxonomic units (OTUs) were identified in the biodynamic plot, while 14,778 OTUs were identified in the organic and 14,298 OTUs in the conventional plot, respectively
In 2011, 19,567 OTUs were identified in the organic plot, 16,576 OTUs in the biodynamic and 14,192 OTUs in the conventional plot, respectively
Summary
Grapevines, cultured on approximately 7.5 million ha in vineyards throughout temperate regions worldwide [1], are hosts for complex communities of microorganisms and arthropods, which can significantly influence both the quantity of the yield as well as the quality of must and wine [2, 3]. To prevent detrimental economic levels of injury inflicted by pathogenic organisms to grapes, different pest management programs and viticultural farming/cultivation systems are applied by the growers. In conventional viticulture growers follow the conceptual framework of integrated pest management (IPM), which includes careful monitoring, preventive cultural practices and, once economic threshold levels are reached, a combination of the use of synthetic pesticides and biological control strategies. Grapes are typically cultivated without the use of chemical fertilizers or synthetic pesticides. Pest and disease management systems in organic viticulture include the application of copper, especially for the control of downy mildew (Plasmopara viticola) or sulphur against powdery mildew (Erysiphe necator). Copper and sulphur applications against grape pathogens are allowed in biodynamic viticulture
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