Quantification of the Changes in Potent Wine Odorants as Induced by Bunch Rot (Botrytis cinerea) and Powdery Mildew (Erysiphe necator)

Abstract

Fungal infections are detrimental for viticulture since they may reduce harvest yield and wine quality. This study aimed to characterize the effects of bunch rot and powdery mildew on wine aroma by quantification of representative aroma compounds using Stable Isotope Dilution Analysis (SIDA). For this purpose, samples affected to a high degree by each fungus were compared with a healthy sample in each case; to this aim, the respective samples were collected and processed applying identical conditions. Thereby, the effects of bunch rot were studied in three different grape varieties: White Riesling, Red Riesling and Gewürztraminer whereas the influence of powdery mildew was studied on the hybrid Gm 8622-3. Analyses revealed that both fungal diseases caused significant changes in the concentration of most target compounds. Thereby, the greatest effects were increases in the concentration of phenylacetic acid, acetic acid and γ-decalactone for both fungi and all grape varieties. Regarding other compounds, however, inconsistent effects of bunch rot were observed for the three varieties studied.

Modifications of Grapevine Berry Composition Induced by Main Viral and Fungal Pathogens in a Climate Change Scenario

“…Studies about effects on aroma compounds are scarce. Calonnec et al (2004) report a decrease of the thiol 3- sulfanylhexan-1-ol (3SH) in Sauvignon blanc wines and high concentrations of lactones (γ-butyrolactone, γ-dodecalactone, and γ-decalactone) similarly to what also observed in Riesling when berries were affected with PM ( Lopez Pinar et al, 2017a , b ).…”

“…Noble rot is used to produce highly valued sweet dessert wines, such as Sauternes, Tokaji Aszu, and Amarone. The positive effects of noble rot are not only due to the concentration of sugar and aroma components through B. cinerea -induced water loss of the berry, but also from an enhanced synthesis of aromatic metabolites and their precursors, such as odorous lactones (γ and δ lactones) and their precursors ( Miklósy and Kerényi, 2004 ; Tosi et al, 2012 ; Stamatopoulos et al, 2014 ; Lopez Pinar et al, 2017a , b ; Stamatopoulos et al, 2018 ). In particular, this has been shown for S-conjugates of glutathione and cysteine, the precursors of varietal thiols reminiscent of citrus, grapefruit/passionfruit, or boxwood aroma.…”

“…Other odorous volatile compounds, such as lactones (γ and δ lactones), furanone, methional, and phenylacetaldehyde, have been found in botrytized berries ( Kikuchi et al, 1983 ; Miklósy and Kerényi, 2004 ; Tosi et al, 2012 ; Stamatopoulos et al, 2014 ; Lopez Pinar et al, 2017a , b ; Stamatopoulos et al, 2018 ). These compounds can contribute in a desirable way to the flavor of sweet wines produced from noble rot-infected grapes ( Schreier et al, 1976 ; Sarrazin et al, 2007 ; Tosi et al, 2012 ).…”

“…Ethyl esters of fatty acids, which contribute to the fermentation aromas of wine, are hydrolyzed by the esterase activity of B. cinerea ( Dubourdieu et al, 1983 ). Moreover, the development of gray mold, associated with abundant sporulation, as well as the presence of spores in the must, leads to the production of mushroom and earthy off-odors in the resulting wines ( La Guerche et al, 2006 ; Lopez Pinar et al, 2017a , b ). Compounds responsible for such off-odors have been identified as 1-octen-3-one, 1-octen-3-ol, 2-heptanol, and 2-octen-1-ol with mushroom notes, or 2-methylisoborneol with strong earthy notes.…”

Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Microbial Ecology and Chemical-Physical Grape Characteristics at Harvest

“…E. necator can cause a reduction in grape yield of up to 45%, as a consequence of smaller diseased berries (Calonnec et al, 2004). In addition, severely infected clusters have higher total acidity than healthy ones, a higher concentration of phenylacetic acid, acetic acid and γ-decalactone, and a lower content of total anthocyanin and 3-mercaptohexanol (Calonnec et al, 2004;Pinar et al, 2017). Downy mildew is caused by the oomycete Plasmopara viticola, affecting the leaves and berries under warm, moist and humid environmental conditions.…”