Sustainable fertilisation of the vineyard in Galicia (Spain)

Viral diseases are a significant cause of both decreased grape quality and vineyard production. Important agents include grapevine leafroll-associated virus (glravs) and grapevine rupestris stem pitting-associated virus (grspav). However, conducting phytosanitary analysis of vineyards for viruses on-site is challenging, and molecular testing is generally expensive.

Oenococcus oeni is the main lactic acid bacteria (LAB) species which conducts the malolactic fermentation (MLF) in wine. During MLF, O. oeni converts malic acid into lactic acid, which modulates wine aroma composition leading to better balanced organoleptic properties. O. oeni is a highly specialized species only detected in environments containing alcohol such as wine, cider or kombucha. Genome analysis of more than 240 strains showed that they form at least 4 main phylogenetic lineages and several sublineages, which are associated with different beverages or types of wines.

Antão Vaz is a Portuguese white grapevine variety grown mainly in the wine-growing regions of Southern Portugal, particularly in the Alentejo, Lisbon and Setúbal peninsula regions. It is a very vigorous and productive variety, giving the wines a strong identity. It needs heat and sunlight and prefers deep and dry soils, which makes it tolerant to scald caused by the high summer temperatures of Southern Portugal. However, this variety is very susceptible to downy mildew, caused by plasmopara viticola, a very destructive disease in years with rainy springs.

Mannoproteins (MPs) are released from the yeast cell wall during alcoholic fermentation and aging on the lees, and influence aspects of wine quality such as haze formation and colour stability. Yet, as this is a slow process with microbiological and sensory risks, the exogenous addition of extracted MPs poses an efficient alternative. While Saccharomyces cerevisiae has long been studied as a prominent source for MPs extraction, their structure and composition greatly differ between yeast species. This may influence their behaviour in the wine matrix and subsequent impact on wine properties. However, although wine yeast species other than S. cerevisiae possibly present an untapped source of MPs, they are still ill-characterised in terms of chemical composition and influence on wine.

Within a research project for simulating the nitrogen turnover in vineyard soils and the nitrogen uptake by the grape vine, a previously developed plant growth model (Nendel and Kersebaum 2004) had to be evaluated. A dataset was obtained from a monitoring experiment at three vineyard sites with different soil types, conducted in the years 2003 and 2004.