Bark and Grape Microbiome of Vitis vinifera: Influence of Geographic Patterns and Agronomic Management on Bacterial Diversity

Abstract

In recent years, the concept of “microbial terroir” has been introduced in the frame of the more renowned notion of “vitivinicultural terroir,’ since several studies demonstrated that wine characteristics are related to regional microbial community compositions. Most of the existing research focused on grape berries microbiota, since it can directly impact wine quality. In this work we studied, for the first time through next-generation sequencing, the epiphytic bacterial community of vine bark and its relationships with grape microbiota. The study was carried out in two Italian wine appellations (situated in different regions) to explore the impact of biogeography, and the influence of two agronomical practices (biodynamic and conventional) was evaluated as well. Overall, our results show that grapevine bark harbors a rich epiphytic microbiota and displays a higher microbial biodiversity than grape berry. Moreover, this study suggests that geographic and anthropogenic factors impact both bark and grape bacteriomes, but to a different extent. The evidence of a “microbial terroir” seems to be even more marked in bark than in berries, possibly due to its permanence over time and to its physical proximity with soil. The importance of vine trunk bark, as potential source of inoculum for grapes and as interesting bacterial diversity habitat, is evidenced. This opens new fields of investigation, not only for researchers that aim at describing this little-known habitat within the vineyard, but also for stakeholders from the wine industry that want to understand the roles of microorganisms on the entire winemaking process, from vineyard to cellar.

Bark from avocado trees of different geographic locations have consistent microbial communities

“…There is limited information on microbial communities of bark from living trees. In this work, avocado tree bark bacterial communities were dominated by representatives of the phyla Actinobacteria, Proteobacteria (in particular, Alphaproteobacteria) and Bacteroidetes, consistently with previous findings in other woody plants, including apple, pear, Ginkgo biloba, wild trees from the Atlantic Rainforest in Brazil, and grapevine (Lambais et al 2014;Leff et al 2015;Arrigoni et al 2018;Vitulo et al 2019;Arrigoni et al 2020). Other phyla observed among the dominant bark microbial communities included Cyanobacteria (only in the Malinalco orchard in this study), Deinococcus-Thremus (in apple and pear), Acidobacteria (in Ginkgo bioloba) and Flavobacteria (in wild trees from the Atlantic Rainforest).…”

“…The importance of the plant compartment as a major determinant of microbial community composition has been previously reported for other plant species, such as Agave spp. (Coleman-Derr et al 2015), vine (Vitulo et al 2019) or tomato (Allard et al 2016). Our results extend these findings to the bark of living trees, and…”

“…Even though the microbial communities from the bark samples from Malinalco and Morelia had highly correlated genus abundances, and were similar in the abundance of many taxonomic groups, they also had important differences, and could be well distinguished based on Bray-Curtis distances. This illustrates that variation can be present in bark environments, when different geographic regions, management practices, times of the year, and tree age, among other factors, are in play, as shown for other plant species (Vitulo et al 2019;Arrigoni et al 2020). The similarities between the microbial communities of bark from the Malinalco and Morelia orchards, suggest there could exist a "core bark microbiome" from avocado trees.…”

“…The bark environment, referred to as caulosphere (Garner, 1967;Nelson, 2018) or dermosphere (Lambais et al 2014), is relatively stable, as compared with leaves, flowers and fruits, which are constantly renovated or appear only seasonally (Vitulo et al 2019). Accordingly, within individual trees, the trunk bark has more diverse communities than newer branches or leaves (Leff et al 2015).…”

Discovering the bacteriome of Vitis vinifera cv. Pinot Noir in a conventionally managed vineyard

“…Indeed, plants should not be considered as single entities, but as a superorganism or a holobiont, resulting from the plant-microorganisms and microbe-microbe interactions 7,8 . In this context, interactions among bacteria and fungi together with physical factors as climate 9 or soil parameters 10,11 , vineyard age 12 , rootstock genotypes 13 , as well as soil management 14,15 and oenological processing 16 , contribute to the determination of a specific terroir 17 . The concept of terroir is based on wine sensory and organoleptic features related to the geographic origin 18 and is defined by the interactions of plants with environmental and human factors 19 .…”