The significance of microbiota in vineyards and wine production

A healthy intestinal flora is essential for avoiding feelings of bloating or constipation. It is often said that the intestine is our second brain because the microbiota present there produce neurotransmitters related to mood. Similarly, it is also crucial for maintaining good immunity and preventing diseases. Interestingly, this is not only true for humans but also for vineyards. Although vineyards do not have intestines, they do contain important microorganisms essential for their health.

In this article, we will discuss technical concepts such as holobiont, microbiota, and microbiome, which are crucial for understanding the world of wine and enhancing the enjoyment of a glass of wine. Read on if you want to discover more about them.

Starting with the Plant

The grapevine is a holobiont plant. But, what does that mean? Perhaps, you have never heard this term associated with wine before, but it is advisable to understand it.

The term 'holobiont' refers to the fact that this plant is a supraorganism, consisting of microbial communities, such as bacteria, fungi, and viruses, that interact with each other and the grapevine. The term was introduced by Lynn Margulis and is derived from the Greek words 'holos,' meaning 'whole,' and 'bios,' meaning 'organism.' It is used to define the association of a macroorganism (such as a human, animal, or plant) and the symbiotic microorganisms that make up its microbiota. Indeed, we, too, are a holobiont organism composed of millions of microorganisms. But, let's focus on the microorganisms in the vineyards.

These microorganisms can regulate essential plant functions such as immunity, so the microbial composition must always be balanced for the plant to be healthy. Conversely, an imbalance of microbial populations could lead to plant deterioration.

This concept is based on four axioms:

• All animals and plants establish symbiotic relationships with microorganisms.
• Symbiotic microorganisms are transmitted from generation to generation.
• The host-symbiont association affects the fitness of the holobiont within its environment.
• Variations in the hologenome result from changes in the host or the microbiota genomes.

For the plant to be healthy, as mentioned before, a balance of plant microbiota, comprising both eukaryotic and prokaryotic microorganisms as well as viruses, must be maintained. The grapevine microbiota exists in both latent and active states in every organ of the plant, from the roots to the aerial parts. Under stress conditions, this symbiotic community can become unbalanced, causing problems in the vineyard.

What Beneficial Properties Do These Microorganisms Have?

Among the microorganisms found in the grapevine tissues, some are beneficial, others are pathogenic, and others are neutral in their interactions within the host. Considering the holobiont concept, we can assume that plant health is intimately linked to the interactions between the plant and its microbiota, similar to the animal kingdom.

Identifying beneficial agents has led to the design of grapevine protection strategies such as biofertilization, biocontrol (the ability to eliminate pathogens), or biostimulation (the ability to synthesize growth-promoting compounds). Some beneficial microbial groups include plant growth-promoting bacteria and arbuscular mycorrhizal fungi.

These plant growth-promoting bacteria can solubilize forms of phosphorus that would otherwise be unavailable to the grapevine. On the other hand, arbuscular mycorrhizal fungi provide increased water absorption capacity to the plant, improving tolerance to water stress and also tolerating soil iron deficiency or salinity.

Exploring Another Term: Microbiome, Leading to a Wide Variety of Wines

The microbiome refers to the community of microorganisms (such as fungi, bacteria, and viruses) that exist in a particular environment. More technically, it is the set of genes contributed by the microbes that form the microbiota within a holobiont.

The environment and different wine-making techniques, such as fertilization, pruning, soil types, or climates, lead to wines with different organoleptic characteristics. These also depend on the wine-making process, the microbial flora associated with the vineyard, and the vineyard's location. This is where the concept of 'terroir' comes into play.

What Is Terroir?

Terroir is a term often challenging to express clearly. It encompasses the biotic and abiotic parameters of a specific region to explain the production of a unique wine. Defining it in a few words is not easy because it comprises many factors, including:

• Temperature or humidity.
• Latitude and altitude.
• Orientation and slope.
• Soil composition.
• Microflora.

Therefore, the definition of terroir also involves characterizing the associated microorganisms, as the yeasts naturally present in the grape in the vineyard, in the winery environment, or inoculated before the fermentation process, significantly impact the final characteristics of the wines. The grape microbiota varies depending on the microclimate variations and available nutritional resources.

As you can see, the microorganisms present in the vineyards are important both for the plant's health and for achieving different organoleptic characteristics in the wines. Good terroir is to wine what a good diet is to humans.

In conclusion, understanding the concepts of holobiont, microbiota, microbiome, and terroir is crucial for appreciating the intricacies of wine production and enjoying a glass of wine to the fullest. Maintaining a balanced microbiota is not only essential for human health but also for the health of grapevines and the quality of the wines they produce.