Abstract
Aim: This research was undertaken in the context of climate change and understanding how rising temperatures may interact with viticultural practices, used to manage fruit exposure in Riesling. An experimental system was designed to passively warm the bunch zone and separate the factors, heat and indirect heat by solar radiation.Methods and results: Field experiments were conducted in 2016 and 2017 at an experimental site located near Rüdesheim in Germany. To increase bunch exposure compared to non-defoliated controls (CON), around 75% of the leaves were removed manually from the bunch zone in an early defoliation treatment at pea size (DEF_E; E-L 31) and later defoliation at véraison (DEF_L, E-L 35). An open heating system (OHS) was installed from pea size stage (E-L 31) onwards. Temperature, light penetration and canopy characterization were determined. Maturity measurements included determination of berry fresh weight, total soluble solids, available primary amino acids (N-OPA), pH, titratable acid and organic acids. For determination of the phenols, berry skin was freeze dried, extracted and analysed by HPLC-PDA.Compared to the same position in the control vine rows, the temperature was more than 10 °C warmer inside the chamber, around 5 °C warmer at the opening of the chamber and at the upper end of the bunch zone, up to 3 °C warmer on a day with high solar radiation. On overcast days there was no temperature difference between these treatments.The OHS treatment affected the ratio of malic and tartaric acid as well as the ratio of glucose and fructose, and produced smaller berries compared to both CON and DEF treatments. Phenols (flavanols, hydroxycinnamic acids, flavonols) in the berry skin were mostly affected by the defoliation. In both years, DEF_E had the highest amount of phenols, followed by the DEF_L. In 2016 OHS had nearly the same concentration of phenols compared to CON. In 2017, the concentrations of phenols were higher in OHS compared to CON.Conclusion: Under future scenarios of increasing temperature conditions, strong changes will be expected for berry maturity parameters. It was found that using an experimental setup to passively heat the bunch zone, malic acid was reduced, smaller berries were produced, and the glucose/fructose ratio changed. For the defoliation treatments, phenol concentrations in berry skin were strongly affected by defoliation and to a lesser extent by higher temperature. Basic maturity parameters were relatively unaffected by defoliation.Significance and impact of the study: Riesling is known for its fruity character and the importance of the sweetness and acidity balance for determining wine style. Under warmer temperature conditions the acidity content will decrease through faster malic acid respiration, impacting the wine´s profile. Higher phenol content could lead to an astringent taste and together with higher protein content, may provide a risk of haze in wine. Neither effect is desirable. In this study, increased bunch exposure following defoliation had a greater effect than temperature alone on phenols. Therefore, the vineyard and canopy management practice will need to be adapted.
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Claims 14
Claim · model-written summary
The open heating system raised temperature by more than 10 °C inside the chamber relative to the same position in control rows.
- Taxon
- Vitis vinifera L. cv. Riesling
Vitis viniferat0 - Treatment
- open heating system (OHS)e1
- Outcome
- temperaturee0
- Direction
- warmere0
- Value
- more than 10 °Ce0
- Comparator
- the control vine rowse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“the temperature was more than 10 °C warmer inside the chamber”
e1“An open heating system (OHS) was installed”
e2“Compared to the same position in the control vine rows”
Claim · model-written summary
Temperature was around 5 °C warmer at the chamber opening and the upper end of the bunch zone than in control rows.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- open heating system (OHS)e1
- Outcome
- temperaturee3
- Direction
- warmere0
- Value
- around 5 °Ce0
- Comparator
- the control vine rowse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“around 5 °C warmer at the opening of the chamber and at the upper end of the bunch zone”
e1“An open heating system (OHS) was installed”
e2“Compared to the same position in the control vine rows”
e3“the temperature was”
Claim · model-written summary
On a day with high solar radiation temperature was up to 3 °C warmer than in control rows.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- open heating system (OHS)e1
- Outcome
- temperaturee3
- Direction
- warmere0
- Value
- up to 3 °Ce0
- Comparator
- the control vine rowse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“up to 3 °C warmer on a day with high solar radiation”
e1“An open heating system (OHS) was installed”
e2“Compared to the same position in the control vine rows”
e3“the temperature was”
Claim · model-written summary
On overcast days there was no temperature difference between the treatments.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- open heating system (OHS)e1
- Outcome
- temperature differencee0
- Direction
- no temperature differencee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“On overcast days there was no temperature difference between these treatments”
e1“An open heating system (OHS) was installed”
Claim · model-written summary
The heating treatment affected the malic-to-tartaric acid ratio and the glucose-to-fructose ratio of the berries.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- OHS treatmente0
- Outcome
- ratio of malic and tartaric acid as well as the ratio of glucose and fructosee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“The OHS treatment affected the ratio of malic and tartaric acid as well as the ratio of glucose and fructose”
Claim · model-written summary
The heating treatment produced smaller berries than both the control and defoliation treatments.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- OHS treatmente1
- Outcome
- smaller berriese0
- Direction
- smallere0
- Comparator
- both CON and DEF treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“produced smaller berries compared to both CON and DEF treatments”
e1“The OHS treatment”
Claim · model-written summary
Berry skin phenols (flavanols, hydroxycinnamic acids, flavonols) were mostly affected by defoliation.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- defoliatione0
- Outcome
- Phenols (flavanols, hydroxycinnamic acids, flavonols) in the berry skine0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“Phenols (flavanols, hydroxycinnamic acids, flavonols) in the berry skin were mostly affected by the defoliation”
Claim · model-written summary
In both years early defoliation gave the highest amount of phenols, followed by late defoliation.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- DEF_Ee0
- Outcome
- amount of phenolse0
- Direction
- higheste0
- Comparator
- DEF_Le0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“In both years, DEF_E had the highest amount of phenols, followed by the DEF_L”
Claim · model-written summary
In 2016 the heating treatment had nearly the same phenol concentration as the control.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- OHSe0
- Outcome
- concentration of phenolse0
- Direction
- nearly the samee0
- Comparator
- CONe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“In 2016 OHS had nearly the same concentration of phenols compared to CON”
Claim · model-written summary
In 2017 phenol concentrations were higher with the heating treatment than in the control.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- OHSe0
- Outcome
- concentrations of phenolse0
- Direction
- highere0
- Comparator
- CONe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“In 2017, the concentrations of phenols were higher in OHS compared to CON”
Claim · model-written summary
Passively heating the bunch zone reduced malic acid.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- passively heat the bunch zonee0
- Outcome
- malic acide0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“using an experimental setup to passively heat the bunch zone, malic acid was reduced”
Claim · model-written summary
Basic maturity parameters were relatively unaffected by defoliation.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- defoliatione0
- Outcome
- Basic maturity parameterse0
- Direction
- relatively unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“Basic maturity parameters were relatively unaffected by defoliation”
Claim · model-written summary
Increased bunch exposure after defoliation had a greater effect on phenols than temperature alone.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Treatment
- increased bunch exposure following defoliatione0
- Outcome
- phenolse0
- Direction
- greater effecte0
- Comparator
- temperature alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“increased bunch exposure following defoliation had a greater effect than temperature alone on phenols”
Claim · model-written summary
The authors conclude that vineyard and canopy management practice will need to be adapted.
- Taxon
- Vitis vinifera L. cv. RieslingVitis viniferat0
- Outcome
- vineyard and canopy management practice will need to be adaptede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Vitis vinifera L. cv. Riesling”
e0“the vineyard and canopy management practice will need to be adapted”
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