Vineyard

Abstract: Grapevine is a well-studied, economically relevant crop, whose associated bacteria could influence its organoleptic properties. In this study, the spatial and temporal dynamics of the bacterial communities associated with grapevine organs (leaves, flowers, grapes, and roots) and soils were characterized over two growing seasons to determine the influence of vine cultivar, edaphic parameters, vine developmental stage (dormancy, flowering, preharvest), and vineyard. Belowground bacterial communities differed significantly from those aboveground, and yet the communities associated with leaves, flowers, and grapes shared a greater proportion of taxa with soil communities than with each other, suggesting that soil may serve as a bacterial reservoir. A subset of soil microorganisms, including root colonizers significantly enriched in plant growth-promoting bacteria and related functional genes, were selected by the grapevine. In addition to plant selective pressure, the structure of soil and root microbiota was significantly influenced by soil pH and C:N ratio, and changes in leaf- and grape-associated microbiota were correlated with soil carbon and showed interannual variation even at small spatial scales. Diazotrophic bacteria, e.g., Rhizobiaceae and Bradyrhizobium spp., were significantly more abundant in soil samples and root samples of specific vineyards. Vine-associated microbial assemblages were influenced by myriad factors that shape their composition and structure, but the majority of organ-associated taxa originated in the soil, and their distribution reflected the influence of highly localized biogeographic factors and vineyard management. IMPORTANCE Vine-associated bacterial communities may play specific roles in the productivity and disease resistance of their host plant. Also, the bacterial communities on grapes have the potential to influence the organoleptic properties of the wine, contributing to a regional terroir. Understanding that factors that influence these bacteria may provide insights into management practices to shape and craft individual wine properties. We show that soil serves as a key source of vine-associated bacteria and that edaphic factors and vineyard-specific properties can influence the native grapevine microbiome preharvest.

Abstract: A long-term (1952-1997) climatology was developed using reference vineyard observations in Bordeaux, France. The procedure partitioned the season into growth intervals from one phenological event to the next (budburst, floraison, veraison, and harvest) in which climatic influences were summed and assessed. The data were then used to investigate the relationships between climate and phenology, berry composition at harvest, total production, and quality. Over the last two decades, the phenology of grapevines in Bordeaux has tended towards earlier phenological events, a shortening of phenological intervals, and a lengthening of the growing season. Merlot and Cabernet Sauvignon varieties have tended to produce higher sugar to total acid ratios, greater berry weights, and greater potential wine quality. Vintage ratings have shown a general increase over the last two decades paralleling the observed phenology and composition trends. The composition and quality trends were mostly described by increases in the number of warm days during floraison and veraison and a reduction in precipitation during maturation. Production variability was not as readily described by phenological-interval climate parameters, but regression modeling did indicate that rainfall during physiologically important periods (flowering and maturation) tended to decrease crop production. By variety, the relationships between phenology, climate, and composition were typically higher (both positive and negative) for Merlot than for Cabernet Sauvignon and could be an indication that, in Bordeaux, Merlot is more phenologically and climatologically sensitive. Additionally, sugar to acid ratios revealed that both Merlot and Cabernet Sauvignon composition influenced Bordeaux wine quality, although variations in Cabernet Sauvignon described substantially more of the variability in ratings. This indicates that the wine industry in Bordeaux is more dependent Cabernet Sauvignon for good vintages than on Merlot.

Abstract: Aims: The impact of water deficit stress on vine shoot growth, berry weight, grape composition and overall vintage quality was investigated in Bordeaux vineyards. Methods for assessing water deficit stress were compared.Methods and results: Vine water status was assessed on three soil types during four vintages by means of stem water potential and carbon isotope discrimination measured on grape sugar. Regional water deficit was compared for a range of over 30 vintages by means of water balance modelling. It was shown that water deficit stress anticipated shoot growth slackening, limited berry weight and enhanced berry anthocyanin content. Berry sugar content was greatest when water deficit was mild. It was shown that stem water potential measurements and carbon isotope discrimination are accurate tools for assessing vine water status at plot scale. Seasonal water deficit at a regional scale can be correctly estimated by water balance models. Vintage quality in Bordeaux is determined by the intensity of water deficit stress rather than by the level of the temperatures.Conclusions: Vine phenology and grape ripening are highly dependent on water uptake conditions. Mild water deficit stress enhances grape quality for the production of red wines. Vine water status can accurately be assessed by means of stem water potential or carbon isotope discrimination measured on grape sugars. Quality losses through severe water stress can be avoided through the use of drought-adapted plant material, appropriate canopy management, yield reduction or the implementation of deficit irrigation.Significance and impact of the study: This study shows the key role of water deficits in the production of quality grapes for red wine production. Methods for assessing vine water status are compared and discussed. Among many existing methods, the accuracy of stem water potential, carbon isotope discrimination measured on grape sugar and water balance modelling are emphasized.