Polish Study Finds Grapevines With 50% Less Fertilizer Produce Wines Richer in Aroma Compounds

A five-year field study in Poland found that grapevines treated with a combination of mycorrhizal inoculants and 50% less mineral fertilizer produced must and wine with higher levels of aroma-related compounds than fully fertilized vines, according to research published Thursday in OENO One.

The study focused on Vitis vinifera “Danmarpa Polonia,” a Polish grapevine selection closely related to the Hungarian cultivar Pannonia Kincse. Researchers Marcin Kolasiński, Mariusz Dziadas and Joanna Bykowska tested whether fungi associated with plant roots could change the formation of volatile compounds and aroma precursors in grapes grown under rainfed conditions.

The work was carried out from late 2018 to 2023 at the University of Life Sciences in Poznań, in western Poland. The vineyard was not irrigated. The trial included 120 plants divided into five treatments, each with three biological replicates. The treatments were ectomycorrhizal inoculation, arbuscular mycorrhizal inoculation, a combination of both inoculations, a fully fertilized control, and a reduced-fertilization control with no inoculation. All inoculated vines received 50% less mineral fertilizer than the standard control.

The main result was that the combined inoculation treatment produced the strongest increase in compounds linked to grape and wine aroma. In must from the 2022 season, the total amount of free volatile compounds reached about 141.14 micrograms per liter equivalents in the dual-inoculated vines. That compared with 76.87 in the arbuscular treatment, 45.53 in the ectomycorrhizal treatment, 27.04 in the reduced-fertilization control, and 16.32 in the fully fertilized control.

The same overall pattern appeared in the 2021 fruit. The combined inoculation treatment again showed the highest total abundance of free volatiles in must, followed by the two single-inoculation treatments, while the fully fertilized control had the lowest total signal.

Among the compounds that stood out in the dual-inoculated must in 2022 were (E)-3-hexen-1-ol at 51.25 micrograms per liter equivalents and geraniol at 27.93. The treatment also produced the highest measured levels of (E)-2-hexenal, citronellol and nerol. These molecules help shape aroma expression in grapes and wine. The study identified nine free volatile compounds in the musts from both 2021 and 2022, including C6 aldehydes, C6 alcohols and monoterpene alcohols.

The researchers also examined glycosidically bound aroma precursors, which are non-volatile compounds stored in grapes and can release aroma-active molecules later during fermentation and aging. After enzymatic hydrolysis of must samples from 2021, the combined inoculation treatment again had the highest amounts of released aglycones across all six compounds measured, including 1-hexanol, (E)-3-hexen-1-ol, (E)-2-hexen-1-ol, alpha-terpineol, citronellol and geraniol. Treatments with only arbuscular inoculation and the fully fertilized control showed intermediate levels, while the ectomycorrhizal-only treatment and the reduced-fertilization control showed the lowest totals.

The paper said wines made from the dual-inoculated vines also had significantly higher total volatile concentrations than the controls. A principal component analysis, a statistical method used to show patterns in complex data, clearly separated the dual-inoculated vines from the control treatments, reinforcing the idea that the combined treatment changed the grapes’ and wines’ aromatic profile.

The findings matter beyond academic plant science because they point to a possible way for wine producers to reduce fertilizer use without sacrificing, and potentially improving, aromatic quality. For the broader beverage industry, especially wineries working on precision viticulture and lower-input farming, the work adds evidence that bioinoculation may become part of efforts to balance sustainability goals with product quality. The study does not prove that the same effect would appear in every vineyard or grape variety, but it gives producers another management tool to watch closely.

The authors placed several limits on their own results. They said arbuscular mycorrhiza in grapevines is well documented, but evidence for true ectomycorrhizal colonization in grapevine roots remains limited. The “ectomycorrhizal” treatment in this trial referred to a commercial inoculum containing ectomycorrhizal fungal isolates and selected basidiomycetes applied according to the manufacturer’s recommendations. Root colonization was not independently measured by microscopic or molecular methods, so the study cannot confirm how much of the observed effect came from established fungal symbiosis in the roots.

That caution is important because the strongest response came from the combined treatment that included both the ectomycorrhizal-type product and the arbuscular inoculum. The authors said the treatment should be interpreted as a practical inoculation variant used in the field, not as direct proof that grapevines formed a verified ectomycorrhizal partnership.

The 2023 growing season was not included in the volatile-compound analysis because severe grapevine powdery mildew under the trial’s low-intervention management prevented a representative fruit harvest. As a result, the aroma findings are based on fruit collected in the third and fourth years after planting, during the 2021 and 2022 seasons.

The study adds to a growing body of work suggesting that root-associated fungi can affect more than nutrient uptake and drought tolerance. The authors said the results support the view that mycorrhizal associations may also influence grapevine secondary metabolism, including pathways tied to terpene formation and other volatile compounds that shape varietal aroma in wine.