 IVES 9 IVES Conference Series 9 Macrowine 9 Macrowine 2021 9 Grapevine diversity and viticultural practices for sustainable grape growing 9 Defoliation timing impacts berry secondary metabolites and sunburn damage

Defoliation timing impacts berry secondary metabolites and sunburn damage

Abstract

Sunburn is a physiological disorder that leads to yield and quality losses in a range of fruits such as grapes and apples. It affects the visual appearance and the composition of the fruit, leading to irreversible changes and ultimately, cell death in extreme situations. Sunburn is caused by a combination of excessive radiation and temperature that lead to photo- and thermal stress, the formation of reactive oxygen species and oxidative stress. A series of factors, such as environmental conditions, grape variety and development stage modulate the final amount of damage. In turn, berries have evolved a series of mechanisms to protect themselves that are dependent on developmental stage [1]. Secondary metabolites such as the carotenoids, polyphenols and even the aroma compounds can act as antioxidants and light screens [2-4], however, the ability to upregulate their production depends on ripening stage [5]. This project aimed to evaluate the changes in secondary metabolism generated by varying degrees of sunburn damage in Chardonnay grapes, and how exposure of berries through defoliation at two different stages in development could modulate sunburn intensity.Field trials were conducted in two vineyards in the Orange region (NSW, Australia) during 2019. Treatments consisted of vines defoliated after the end of flowering, at véraison, and a non-defoliated control. Basic chemistry, carotenoids, polyphenols and free volatile analysis were conducted. Canopy mesoclimate, ultraviolet and photosynthetically active radiation, as well as berry temperature and radiation were monitored throughout the season using a range of sensors and light sensitive tapes.Sunburn damage was modulated by the specific meteorological conditions at each vineyard, and was higher at the warmest vineyard. Changes in grape composition were statistically significant between the different levels of sunburn damage, all of which could be clearly separated using MB-SO-PLS-LDA analysis. Among four different levels of damage studied, undamaged berries were the most distinct category and contained the highest levels of terpenes and lowest levels of polyphenols. As sunburn damage increased, an upregulation of compounds from the xanthophyll cycle was observed as well as of the flavonoids and flavan-3-ols, while a distinct destruction of chlorophyll a and b was also evident. Changes to concentrations of terpenes seemed to be mainly affected by temperature than radiation, and changes to specific aroma compounds such as the GLVs are reported for the first time. Comparison of defoliation treatments revealed that late defoliation led to a higher level and intensity of sunburn damage. Distinct biosynthetic mechanisms were apparent with regards to defoliation timing.

DOI:

Publication date: September 2, 2021

Issue: Macrowine 2021

Type: Article

Authors

Joanna Gambetta, Leigh M. Schmidtke, Bruno Holzapfel

Charles Sturt University – Faculty of Science; University of Adelaide, School of Agriculture, Food and Wine; South Australian Research and Development Institute, School of Agricultural and Wine Sciences, National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia, School of Agricultural and Wine Sciences, National Wine and Grape Industry Centre, New South Wales Department of Primary Industries, Wagga Wagga, NSW 2650, Australia

Contact the author

Keywords

sunburn, leaf removal, chardonnay, carotenoids, polyphenols, aroma compounds

Citation

Short-term relationships between climate and grapevine trunk diseases in southern French vineyards

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The interplay between grape ripening and weather anomalies – A modeling exercise

Current climate change is increasing inter- and intra-annual variability in atmospheric conditions leading to grapevine phenological shifts as well altered grape ripening and composition at ripeness. This study aims to (i) detect weather anomalies within a long-term time series, (ii) model grape ripening revealing altered traits in time to target specific ripeness thresholds for four Vitis vinifera cultivars, and (iii) establish empirical relationships between ripening and weather anomalies with forecasting purposes. The Day of the Year (DOY) to reach specific grape ripeness targets was determined from time series of sugar concentrations, total acidity and pH collected from a private company in the period 2009-2021 in North-Eastern Italy. Non-linear models for the DOY to reach the specified ripeness thresholds were assessed for model efficiency (EF) and error of prediction (RMSE) in four grapevine cultivars (Merlot, Cabernet Sauvignon, Glera and Garganega). For each vintage and cultivar, advances or delays in DOY to target specified ripeness thresholds were assessed with respect to the average ripening dynamics. Long-term meteorological series monitored at ground weather station by means of hourly air temperature and rainfall data were analyzed. Climate statistics were obtained and for each time period (month, bimester, quarter and year) weather anomalies were identified. A linear regression analysis was performed to assess a possible correlation that may exist between ripening and weather anomalies. For each cultivar, ripeness advances or delays expressed in number of days to target the specific ripening threshold were assessed in relation to registered weather anomalies and the specific reference time period in the vintage. Precipitation of the warmest month and spring quarter are key to understanding the effect of climate change on sugar ripeness. Minimum temperatures of May-June bimester and maximum temperatures of spring quarter best correlate with altered total acidity evolution and pH increment during the ripening process, respectively.

Influence of a spontaneous cover crop on the vineyard and soil erosion under Mediterranean climate

Sixty five % of the agricultural area of the Basque Country located in the DO Ca Rioja corresponds to vineyards. More than 40% of it has an average slope greater than 10%, which makes it sensitive to erosive processes. Furthermore, it is foreseeable that extreme weather events (storms, hail, extreme heat and cold, etc.) will be favored due to climate change. Cover cropping can mitigate this risk, and therefore the objective of this work is to evaluate the impact that a vegetable cover has on the agronomic behavior of the vineyard, the quality of the grape and soil erosion. For this, a trial has been carried out with a Graciano variety vineyard with a slope between 10% -20% during the years 2020 and 2021. Conventional tillage management in the area has been compared (4-6 passes per year of tillage machinery) versus spontaneous vegetation cover management in the vineyard. This implies not tilling and allowing the grass of the land to colonize the range between the lines of vines, controlling their height through 1-3 mowing passes per year, always trying to affect the surface of the land as little as possible. The vegetative growth, yield and quality of the grape and wine was measured. Furthermore, erosion has been measured using Gerlasch boxes. The yield was lower in the second year of the trial in the cover crop treatment, but erosion was significantly reduced.

Second pruning as a strategy to delay maturation in cv. ‘Touriga nacional’ in the Portuguese Douro region

The advance in maturation of wine grapes is an important climate change risk related effect that could affect warm regions like Portuguese Douro Wine Region. Indeed, the climate analysis over the past years registered a decrease in the precipitation, significant higher average temperatures, and a more frequent occurrence of extreme weather events, including heat waves. In these conditions the length from anthesis until maturation is shortened and the uncoupling of technical and phenolic maturity results in berries with higher sugar concentration (and lower acidity), but lower anthocyanins, tannins, and total phenolic concentration, which produce unbalanced wines.
In this work, an innovative strategy of crop forcing, based on forcing vine regrowth after a second pruning of green shoots, was tested, aimed at delaying ripening until the temperature becomes lower and, therefore, preventing acidity loss and increasing anthocyanin-to-sugar ratio. The experiments were conducted in 2019 and 2020 in a commercial vineyard of ‘Touriga Nacional’ located in the Douro Region. Crop forcing was conducted 15 (CF1) to 30 (CF2) days after fruit set. Vines pruned with conventional methods were used as control (CF0). Results confirmed that fruit ripening was shifted from the hot season (August/September), until a cooler period (October through early-November). At harvest, grapevine berries from CF1 and CF2 presented lower pH and higher acidity, than control, with no significant differences in colour intensity and phenolic levels composition. Sugar content was lower in CF2-treated vines in both seasons. However, in CF-treated vines the number and size of clusters were significantly lower (up to 88% reduction) than in control plants. A metabolomics analysis of mature berries from CF-treated vines and control is underway. Crop forcing was indeed effective in producing a more balance berry composition but severely reduced grapevine yield,

Permanent cover cropping with reduced tillage increased resiliency of wine grape vineyards to climate change

Majority of California’s vineyards rely on supplemental irrigation to overcome abiotic stressors. In the context of climate change, increases in growing season temperatures and crop evapotranspiration pose a risk to adaptation of viticulture to climate change. Vineyard cover crops may mitigate soil erosion and preserve water resources; but there is a lack of information on how they contribute to vineyard resiliency under tillage systems. The aim of this study was to identify the optimum combination of cover crop sand tillage without adversely affecting productivity while preserving plant water status. Two experiments in two contrasting climatic regions were conducted with two cover crops, including a permanent short stature grass (P. bulbosa hybrid), barley (Hordeum spp), and resident vegetation under till vs. no-till systems in a Ruby Cabernet (V. vinifera spp.) (Fresno) and a Cabernet Sauvingon (Napa) vineyard. Results indicated that permanent grass under no-till preserved plant available water until E-L stage 17. Consequently, net carbon assimilation of the permanent grass under no-till system was enhanced compared to those with barley and resident vegetation. On the other hand, the barley under no-till system reduced grapevine net carbon assimilation during berry ripening that led to lower content of nonstructural carbohydrates in shoots at dormancy. Components of yield and berry composition including flavonoid profile at either site were not adversely affected by factors studied. Switching to a permanent cover crop under a no-till system also provided a 9% and 3% benefit in cultural practices costs in Fresno and Napa, respectively. The results of this work provides fundamental information to growers in preserving resiliency of vineyard systems in hot and warm climate regions under context of climate change.