 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

VineyardFACE: Investigation of a moderate (+20%) increase of ambient CO2 level on berry ripening dynamics and fruit composition

Climate change and rising atmospheric carbon dioxide concentration is a concern for agriculture, including viticulture. Studies on elevated carbon dioxide have already been on grapevines, mainly taking place in greenhouses using potted plants or using field grown vines under higher CO2 enrichment, i.e. >650 ppm. The VineyardFACE, located at Hochschule Geisenheim University, is an open field Free Air CO2 Enrichment (FACE) experimental set-up designed to study the effects of elevated carbon dioxide using field grown vines (Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon). As the carbon dioxide fumigation started in 2014, the long term effects of elevated carbon dioxide treatment can be investigated on berry ripening parameters and fruit metabolic composition.
The present study aims to investigate the effect on fruit composition under a moderate increase (+20%; eCO2) of carbon dioxide concentration, as predicted for 2050 on both Riesling and Cabernet Sauvignon. Berry composition was determined for primary (sugars, organic acids, amino acids) and secondary metabolites (anthocyanins). Special focus was given on monitoring of berry diameter and ripening rates throughout three growing seasons. Compared to previous results of the early adaptative phase of the vines [1], our results show little effect of eCO2 treatment on primary metabolites composition in berries. However, total anthocyanins concentration in berry skin was lower for eCO2 treatment in 2020, although the ratio between anthocyanins derivatives did not differ.
[1] Wohlfahrt Y., Tittmann S., Schmidt D., Rauhut D., Honermeier B., Stoll M. (2020) The effect of elevated CO2 on berry development and bunch structure of Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon. Applied Science Basel 10: 2486

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Late season canopy management practices to reduce sugar loading and improve color profile of Cabernet-Sauvignon grapes and wines in the high irradiance and hot conditions of California Central Valley

Global warming is accelerating grape ripening, leading to unbalanced wines from fruit with high sugar content but poor aroma and colour development. Reducing the size of the photosynthetic apparatus after veraison has been shown to delay technological ripeness in cool climates, but methods have not been tested in areas with high irradiance and temperature where fruit exposure could have disastrous effects on berry composition. In this Cabernet-Sauvignon trial, we compared the application of an antitranspirant (pinolene), to severe canopy topping and above bunch zone leaf removal, all performed at mid-ripening, with an untouched control. We monitored the vines weekly by measuring stem water potential, gas exchange, fruit zone light exposure. We sampled berries to measure berry weight, total soluble solids, pH, titratable acidity, and the anthocyanin profile. At harvest, we assessed yield components, measured carbon isotope discrimination, rated sunburn on clusters, and produced experimental wines. We submitted harvest samples to metabolomic profiling through PFP-Q Exactive MS/MS and wines to sensory analysis. Application of the antitranspirant significantly reduced stomatal conductance and assimilation rate but did not affect the stem water potential. Inversely, leaf removal and topping increased water potential but did not affect leaf gas exchange. The late topping was the only treatment able to decrease sugar content (up to 2Bx), increase titratable acidity and pH, and improve anthocyanin content because of lower degradation of di-hydroxylated forms. Late leaf removal above the bunch zone increased lightning conditions in the canopy and produced the most significant damage on fruits. Yield components were not affected. This work suggests that late-season canopy management can effectively control ripening speeds and improve grapes and wines. Still, the effect on grape exposure in a critical time must be well balanced to avoid problems with the appropriate technique.

Assessment of climate change impacts on water needs and growing cycle on grapevine in three DOs of NE Spain

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In recent decades, the scarcity of water resources in agriculture in certain areas has been aggravated by climate change, which has caused an increase in temperatures, changes in rainfall patterns, as well as an increase in the frequency of extreme phenomena such as droughts and heat waves. Although the vine is considered a drought-tolerant specie, it has to satisfy important water requirements to complete its cycle, which coincides with the hottest and driest months. Achieving sustainable viticulture in this scenario requires high levels of efficiency in the use of water, a scarce resource whose use is expected to be severely restricted in the near future. In this regard, the use of drought-tolerant varieties that are able to maintain grape yield and quality could be an effective strategy to face this change. During three consecutive seasons (2018-2020) the behavior in rainfed regime of 13 traditional red grapevine varieties of the Spain central region was studied. These varieties were cultivated in a collection at Centro de Investigación de la Vid y el Vino de Castilla-La Mancha (IVICAM-IRIAF) located in Tomelloso (Castilla-La Mancha, Spain). Yield components (yield, mean bunch and berry weight, pruning weight), physicochemical parameters of the musts (brix degree, total acidity, pH) and some physiological parameters related with water stress during ripening period (δ13C, δ18O) were analysed. The application of different statistical techniques to the results showed the existence of significant differences between varieties in their response to stressful conditions. A few varieties highlighted for their high ability to adapt to drought, being able to maintain high yields due to their efficiency in the use of water. In addition, it was possible quantify to what extent climate can be a determinant in the δ18O of musts under severe water stress conditions.