Macrowine 2021
IVES 9 IVES Conference Series 9 Changes in grape-associated microbiome as a consequence of post-harvest withering

Changes in grape-associated microbiome as a consequence of post-harvest withering

Abstract

AIM: Grape withering is an oenological post-harvest process used for production of reinforced and sweet wines. Drying can be carried out by keeping the ripe grape in traditional large, well-aired rooms (non-controlled environment) or, more and more often, in a warehouse under controlled conditions of airflow and relative humidity (controlled environment)[1]. The microbiome associated with withering grapes has been showed to be profoundly linked with the process and its results[2,3]. The main aims of this study were to (a) provide detailed information on bacterial and fungal communities evolution throughout the grapes withering process, and (b) perform a comparative study between two dehydration methods, regarding the associated microbiomes.

METHODS: Samples of withering grapes were collected in the Italian viticultural zone Valpolicella, where the renowned wine Amarone is produced using non-botrytized withered grapes of Corvina variety. Two different post-harvest conditions were analyzed (non-controlled and controlled withering environment); grapes coming from two vineyards (close but differing for soil characteristics) were considered, during 2 subsequent vintages. To map the microbiome during withering, Next-Generation Sequencing (NGS) was employed[4]: the progression of fungal and bacterial species was characterized through metabarcoding (ITS and 16s) at 4 different time points (from 0 to 30% of weight loss).

RESULTS: No significant differences, at biodiversity level, were found between the microbial communities of grapes from the two vineyards, nor between the two vintages. The evolution of microorganisms during drying was instead interestingly variable. Moreover, slight but significant differences were found between the two withering systems, although significant only for some taxa.

CONCLUSIONS: NGS metabarcoding showed to be an effective technique in the study of withering-grape microbiome and provided new information on the changes occurring in microbial communities because of the drying process. Indeed, to our knowledge, the present work is the first time-course study of both mycobiome and bacteriome throughout withering. The study also showed that changes of drying conditions can lead to significant modifications of the berry-skin microbiota.

DOI:

Publication date: September 3, 2021

Issue: Macrowine 2021

Type: Article

Authors

Tiziana Nardi, Luca Nerva*, Walter Chitarra*

CREA – Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di Ricerca Viticoltura ed Enologia, Conegliano, Italy, Diego Tomasi and Tiziana Nardi  CREA – Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di Ricerca Viticoltura ed Enologia, Conegliano, Italy *these authors contributed equally to the work

Contact the author

Keywords

Post-harvest, grape microbiome, metabarcoding, epiphytes

Citation

Related articles…

Impact on leaf morphology of Vitis vinifera L. cvs Riesling and Cabernet Sauvignon under Free Air Carbon dioxide Enrichment (FACE)

Atmospheric carbon dioxide (CO2) concentration has continuously increased since pre-industrial times from 280 ppm in 1750, and is predicted to exceed 700 ppm by the end of 21st century. For most of C3 plant species elevated CO2 (eCO2) improve photosynthetic apparatus results in an increased plant biomass production. To investigate the effects of eCO2 on morphological leaf characteristics the two Vitis vinifera L. cultivars, Riesling and Cabernet Sauvignon, grown in the Geisenheim VineyardFACE (Free Air Carbon dioxide Enrichment) system were used. The FACE site is located at Geisenheim University (49° 59′ N, 7° 57′ E, 94 m above sea level), Germany and was implemented in 2014 comparing future atmospheric CO2-concentrations (eCO2, predicted for the mid-21st century) with current ambient CO2-conditions (aCO2). Experiments were conducted under rain-fed conditions for two consecutive years (2015 and 2016). Six leaves per repetition of the CO2 treatment were sampled in the field and immediately fixed in a FAA solution (ethanol, H2O, formaldehyde and glacial acetic acid). After 24 h leaf samples were transferred and stored in an ethanol solution. Subsequently, leaf tissue was dehydrated using ethanol series and embedded in paraffin. By using a rotary microtomesections of 5 µm were prepared and fixed on microscopic slides. Subsequent the samples were stained using consecutive staining and washing solutions. Afterwards pictures of the leaf cross-sections were taken using a light microscope and consecutive measurements were conducted with an open source image software. Differences found in leaf cross-sections of the two CO2 treatments were detected for the palisade parenchyma. Leaf thickness, upper and lower epidermis and spongy parenchyma remained less affected under eCO2 conditions. The observed results within grapevine leaf tissues can provide first insights to seasonal adaptation strategies of grapevines under future elevated CO2 concentrations.

Effects of graft quality on growth and grapevine-water relations

Climate change is challenging viticulture worldwide compromising its sustainability due to warmer temperatures and the increased frequency of extreme events. Grafting Vitis vinifera L.

Influence of weather and climatic conditions on the viticultural production in Croatia

The research includes an analysis of the impact of weather conditions on phenological development of the vine and grape quality, through monitoring of four experimental cultivars (Chardonnay, Graševina, Merlot and Plavac mali) over two production years. In each experimental vineyard, which were evenly distributed throughout the regions of Slavonia and The Croatian Danube, Croatian Uplands,

Terroir analysis and its complexity

Terroir is not only a geographical site, but it is a more complex concept able to express the “collective knowledge of the interactions” between the environment and the vines mediated through human action and “providing distinctive characteristics” to the final product (OIV 2010). It is often treated and accepted as a “black box”, in which the relationships between wine and its origin have not been clearly explained. Nevertheless, it is well known that terroir expression is strongly dependent on the physical environment, and in particular on the interaction between soil-plant and atmosphere system, which influences the grapevine responses, grapes composition and wine quality. The Terroir studying and mapping are based on viticultural zoning procedures, obtained with different levels of know-how, at different spatial and temporal scales, empiricism and complexity in the description of involved bio-physical processes, and integrating or not the multidisciplinary nature of the terroir. The scientific understanding of the mechanisms ruling both the vineyard variability and the quality of grapes is one of the most important scientific focuses of terroir research. In fact, this know-how is crucial for supporting the analysis of climate change impacts on terroir resilience, identifying new promised lands for viticulture, and driving vineyard management toward a target oenological goal. In this contribution, an overview of the last findings in terroir studies and approaches will be shown with special attention to the terroir resilience analysis to climate change, facing the use and abuse of terroir concept and new technology able to support it and identifying the terroir zones.

Upscaling the integrated terroir zoning through digital soil mapping: a case study in the Designation of Origin Campo de Borja

homogeneous zones by intersecting several partial zonings of major factors that influence vineyard growth. Each of them follows specific process from their corresponding disciplines. Soil zoning specifically refers to a Soil Resource Inventory map that has traditionally been generated by conventional soil mapping methods. These methods have shortcomings in reaching fine cartographic and categorical details and involve significant expenses, which undermines their applicability. A new framework named Digital Soil Mapping has introduced quantitative models by statistical techniques to establish soil-landscape relationships and is able to provide intensive scale cartography.

In the present study, a microzoning at 1:10.000 scale is generated from an initial zoning, where the conventional soil map with polytaxic map units is replaced by a new one from digital techniques that disaggregates them. The comparison between the zonings considers a quantitative evaluation of capability for each Homogeneous Terroir Unit by means of the Viticultural Quality Index and its categorization based on its distribution by map. The spatial intersection of both maps gives rise to a confusion matrix in which the flows of class variations after the substitution are assessed.

The results show a five-fold increase in the number of Homogeneous Terroir Units identified and a larger differentiation among them, evidenced by a wider range in the capability index distribution. Both elements are accompanied by an increase in the detection of areas of higher potential within previously undervalued uniform zones.These features are a direct effect of the improvements brought by Digital Soil Mapping techniques and would verify the advantages of their implementation in the Integrated Terroir zoning. Eventually, such new highly detailed terroir units would benefit precision viticulture and sustainable management practices.