South Africa Wine Research Projects 2025

PROJECTS 2025 RESEARCH

RESEARCH, DEVELOPMENT AND INNOVATION

www.sawine.co.za

TABLE OF CONTENTS

1 FOREWORD ____________________________________________2

2 VITICULTURE RESEARCH __________________________________3 2.1 Grapevine protection – Insects and pests _ __________________4 2.2 Grapevine protection – Fungi and bacteria ___________________8 2.3 Soil and water _______________________________________ 12 2.4 Cultivation __________________________________________ 22 2.5 Terroir _____________________________________________ 26 2.6 Grapevine improvement _ ______________________________ 30

3 OENOLOGY RESEARCH _ ________________________________ 43 3.1 Wine improvement _ __________________________________ 44

4 TECHNOLOGY TRANSFER ________________________________ 58

SOUTH AFRICA WINE RESEARCH 2025

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1 FOREWORD

The South African wine industry continues to navigate an era marked by rapid transformation, global uncertainty, and a growing emphasis on sustainability and innovation. In this dynamic context, South Africa Wine remains steadfast in its mission to support a resilient, competitive, and future-ready wine sector. With increasingly stringent Environmental, Social, and Governance (ESG) expectations, the evolving global marketplace demands forward-thinking strategies that integrate research, innovation, technology and collaboration. At the heart of this mission lies the South Africa Wine Research, Development, and Innovation (RDI) strategy. In 2025, this strategy has gained even greater momentum, driving impactful initiatives that address critical issues such as climate adaptation, water use efficiency, soil and vine health, wine authenticity, and sustainable farming practices. We have continued to champion flagship programmes that merge scientific excellence with practical relevance, aiming to deliver tangible benefits for the entire value chain. This year’s research booklet provides a curated overview of new, ongoing, and completed research projects as of 2025. It showcases the efforts of dedicated researchers, alongside academic institutions, producers, and winemakers, who are shaping a sustainable future for South African wine. The projects outlined here reflect our deep commitment to evidence-based innovation, knowledge transfer, and global collaboration. As we look ahead, we invite all stakeholders to engage with this work—to inspire, learn, and build a wine industry that thrives economically, environmentally and socially.

Sincerely, South Africa Wine Research, Development and Innovation Team

OUR TEAM GERARD MARTIN: RDI Executive (gerard@sawine.co.za) ANEL ANDRAG: RDI Manager – Viticulture (anel@sawine.co.za) DR ADRIAAN OELOFSE: RDI Manager – Oenology (adriaan@sawine.co.za)

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SOUTH AFRICA WINE RESEARCH 2025

2 VITICULTURE RESEARCH

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2. VITICULTURE RESEARCH NEW PROJECT

2.1 GRAPEVINE PROTECTION – INSECTS AND PESTS

RISK MANAGEMENT SYSTEM FOR DROSOPHILA SUZUKII TO INFORM MANAGEMENT DECISIONS AT DIFFERENT SPATIAL SCALES

SU EE PA 25-01 Prof Pia Addison, Department of Conservation Ecology and Entomology, Stellenbosch University Start date: 2025

AIM AND INDUSTRY RELEVANCE: Unlike other Drosophilidae (vinegar flies), Drosophila suzukii or Spotted Wing Drosophila (SWD) females can cause significant damage to soft-skinned fruit such as wine- and table grapes, stone fruit and soft berries like blue- and raspberries due to the ability to damage healthy and undamaged fruit by using a serrated ovipositor and lay their eggs. Due to a lack of knowledge of the risk SWD poses to the fruit industry, this project aims to develop a risk management system to assist the fruit industry in decision-making on a geographical scale. The project will generate new information on the fruit/cultivar/variety susceptibilities to SWD and determine alternate host status, distribution and phenology in production areas. GIS and Data CoOp integration will bring about regular, up-to-date risk maps after demographic changes of SWD in different fruit and cultivar types and climates are monitored.

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2. VITICULTURE RESEARCH NEW PROJECT

EXPLORING INTEGRATED PEST MANAGEMENT PRACTICES FOR DROSOPHILA SUZUKII IN SOUTH AFRICA

SU EE PA 25-02 Prof Pia Addison, Department Conservation Ecology and Entomology, Stellenbosch University Start date: 2025

AIM AND INDUSTRY RELEVANCE: Drosophila suzukii (Matsumura), the spotted wing drosophila (SWD), can damage several soft skinned fruits, including cherries, grapes, blueberries and stone fruit. They are indigenous to Asia, and unlike other vinegar flies, the female D. suzukii can lay eggs in whole and intact ripening fruit using a serrated ovipositor. Due to the short generation cycle of D. suzukii , crops are at risk close to harvest, when chemical interference may not be possible due to potential residues left behind. The project aims to use integrated pest management to explore and assess biological control as an alternative for managing D. suzukii in South Africa. • Commence and maintain a SWD colony for laboratory studies. • Development of attractants for use in SWD management. • Evaluate currently available commercial attractants in attract and kill applications for SWD in South Africa. • Assess the diversity of parasitoids within the Drosophilidae family. • Screen potential entomopathogenic- nematodes and fungicides against SWD in laboratory bioassays. The steps included to achieve the outcome are as follows:

SOUTH AFRICA WINE RESEARCH 2025

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

ESTABLISHING A BARCODING DATABASE OF LOCAL PESTS OF DECIDUOUS FRUIT

SU-EE PA 23-01 Prof Pia Addison, Department of Conservation Ecology and Entomology, Stellenbosch University Start date: 2023

AIM AND INDUSTRY RELEVANCE: This project aims to develop new knowledge regarding South African pests and to have an ac curate, repeatable and rapid identification method for such pests to ensure market access and good management. Morphological identifications of insects can be problematic when dealing with immature stages or species complexes, such as with the banded fruit weevil complex and fruit flies ( Ceratitis rosa and Ceratitis quilicii ). Immature insects (e.g. fruit-fly larvae) must be reared first since morphological identifications can only be made with adult insects. With validated sequencing, where pest insects are identified by taxonomists and sequenced molecularly, it will be possible to establish a reference database for South African pest insects, especially those that are local and barcoding sequences are not available. South Africa is experiencing a shortage of taxonomists for various insect groups, which means there will be no experts available for morphological insect identifications in the future, as very few people are being trained to take over. Accurate insect identifications significantly impact the management of pests, specifically those of quarantine significance, since incorrect identifications lead to loss of access and financial implications for growers. The outcome of this project will allow for easier identifications by people not trained as Entomol ogists. It is critical, however, to establish a good morphological base on which to make these sequences available.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

THE ECOLOGY OF LOBESIA VANILLANA IN WINE GRAPE VINEYARDS, WITH EMPHASIS ON MANAGEMENT OPTIONS

US ENT 17-A3 Prof Pia Addison, Department Conservation Ecology and Entomology, Stellenbosch University Start date: 2016

AIM AND INDUSTRY RELEVANCE: Lobesia vanillana is a pest species that was recently confirmed to attack wine grapes in the Western Cape. Grapes have not been listed as a host for this pest, therefore we know nothing of its ecology in vineyards. Preliminary observations have indicated that this could be a severe, direct pest that appears to be expanding its host and geographic range. The project aims to address the following questions: 1) What are the most efficient trapping systems to use for monitoring Lobesia , 2) What chemical and biological management practices could be applied to control its populations and, 3) What is the basic life cycle and ecology of L.vanillana in South African vineyards. Apart from taxonomic literature and one host list, excluding samples from the Western Cape, no information is available for L. vanillana . The aim of this study is therefore to obtain data on basic ecology and possible management, with focus on biological control, to develop an initial management strategy.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

2.2 GRAPEVINE PROTECTION – FUNGI AND BACTERIA

BREEDING WINE GRAPES RESISTANT TO POWDERY AND DOWNY MILDEW

P04000058 Ms Phyllis Burger, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC Infruitec-Nietvoorbij

Start date: 2014 Flagship Project

AIM AND INDUSTRY RELEVANCE: The aim, ultimately, is to breed new, high yielding cultivars, that will produce high quality V. vinifera type wine and have tolerance to downy and/or powdery mildew and/or to Botrytis under local conditions. In this project crosses are made to develop cultivars with disease tolerance and good crop and wine making characteristics. Objectives of the project include: • Screening of seedlings obtained from crosses for tolerance to downy and powdery mildew; • Identifying potential parents with disease tolerance and suitable qualities to be used in crosses; • Making crosses, stratifying and germinating seeds; • Developing and establishing seedlings in tunnels and older plants in vineyards; • Identifying and importing cultivars with tolerance to fungal diseases, if possible.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

THE PRACTICAL IMPACT OF SEXUAL REPRODUCTION OF GRAPEVINE POWDERY MILDEW ON REDUCED FUNGICIDE SENSITIVITY

P04000325 Dr Minette Havenga, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC Infruitec-Nietvoorbij Start date: 2023

AIM AND INDUSTRY RELEVANCE: This project will develop new knowledge regarding the primary inoculum, dominant reproductive strategy and basic biology of the powdery mildew fungus. Factors that will be evaluated include environmental requirements, the level of reduced sensitivity to DMI and QoI fungicides in South African vineyards and the effect of post-harvest application on chasmothecia development. Powdery mildew causes serious economic damage in all grape-growing regions. Only a few sexual structures (chasmothecia) were observed in 1996-1999 in Stellenbosch. Since 2015, high num bers of chasmothecia have been common on leaves at the later stages of the growing season in Western Cape vineyards. Sexual reproduction may lead to better-adapted individuals that are less responsive to fungicides. Due to climate change, Western Cape springs are becoming wetter. During bud break, conditions are now more favourable for releasing sexual spores. Asexual and sexual reproduction require different conditions, yet the primary inoculum for the infection is unknown. Therefore, disease models cannot effectively predict fungicide timing. In dustry experts suspect reduced sensitivity to QoI and DMIs. The project aims to determine the primary inoculum source, the level of reduced sensitivity and the effect of sexual reproduction on reduced sensitivity. The project aims not to determine whether specific products have a reduced efficacy but to evaluate biological factors contributing to decreased management. The results will provide information to calibrate prediction models accurately to the environmental requirements of the dominant reproductive system, which will increase the efficacy of fungicide spray programmes and reduce overall fungicide use.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

NEW PRUNING WOUND PROTECTION STRATEGIES AGAINST TRUNK PATHOGENS IN ROOTSTOCK MOTHER VINES

P04000333 Dr Minette Havenga, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC Infruitec-Nietvoorbij Start date: 2023

AIM AND INDUSTRY RELEVANCE: A previous project (P04000108) concluded that rootstock mother vine pruning wounds remained susceptible to Phaeomoniella chlamydospora infections for up to 42 days after pruning. Although several chemical, biological and chemical + biological treatments reduced P. chlamydospora inci dences in artificially inoculated Ramsey and 101-14 Mgt. pruning wounds, the study recommended that more pathogens and rootstock varieties be investigated. Fungicide mixtures will also have to be evaluated to broaden the efficacy of treatments to protect vines against the onslaught of several pathogen groups that all differ in their sensitivity towards fungicides. The use, availability and range of fungicides are under increased pressure worldwide. The search for alternative or biological control agents is crucial to securing sustainable grape production and market access. The study aims to evaluate chemical and biological control agents in various combinations to provide effective pruning wound protection against a range of grapevine trunk pathogens to pro duce high-quality propagation material. There is no published literature on the use of chemicals or biological control agents on rootstock (Vitis spp.) pruning wounds. All previous studies were done on wounds in vineyards (Vitis vinifera) and were not always tested against a wide range of grapevine trunk disease pathogens. The duration of rootstock wound susceptibility across a wide range of grapevine trunk disease pathogens is unknown in SA and worldwide. The benefit of the project to the industry will be a significant contribution towards producing high-quality grapevine propagation material that will contribute to higher take percentages in grapevine nurseries and better establishment of young vines in new vineyards.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

FORMULATION AND EVALUATION OF MICROBIAL CONSORTIA FOR BIOLOGICAL CONTROL OF GRAPEVINE FUNGAL PATHOGENS SAGWRI ES 22-01 Prof Evodia Setati, South African Grape and Wine Research Institute, Stellenbosch University Project is co-funded by the Department of Science and Innovation and the National Research Foundation Start date: 2022 AIM AND INDUSTRY RELEVANCE: The study’s main objective is to construct yeast-bacterial consortia that have antifungal activity against grey rot and mildew disease agents in grapevines and can be used as biocontrol agents. Existing biocontrol agents are mainly single species formulations which are sometimes ineffective under varying environmental conditions. Globally, there is growing interest in reducing the number of chemical fungicides used to control grapevine pathogens such as Botrytis cinerea , Plasmopara viticola and Erysiphe necator . Alternative biological formulations comprising microbial strains are commercially available for use in vineyards. However, not all of them work effectively and consistently under varying field conditions. Consequently, further research is necessary to identify new biological agents with higher efficacy. In the current study, we aim to generate multi-species microbial consortia for the biological control of bunch rot, powdery mildew and downy mildew. Existing biological control agents are based on single microbial species. We believe that multi-species consortia comprising strains with different modes of action that grow optimally under different environmental conditions will offer more efficacy in field conditions. By selecting organisms that do not negatively affect wine fermentation and are tolerant to chemical fungicides currently in use, we believe we can generate biological control agents that can complement existing fungicide spray programs and reduce chemical fungicide use.

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2. VITICULTURE RESEARCH NEW PROJECT

2.3 SOIL AND WATER

EVALUATION OF SOIL HEALTH INDICATORS IN THE STELLENBOSCH WINE GRAPE REGION

SU SS AH 25-01 Prof Ailsa Hardie-Pieters, Department of Soil Science, Stellenbosch University Start date: 2025

AIM AND INDUSTRY RELEVANCE: Soil health is challenging for growers to manage due to limited scientific research available on the topic, particularly in commercial vineyards in South Africa. Although numerous soil health tests are available to growers, their importance to winegrape production is unclear, and there is no benchmark for these indicators. The project goal is to assess the relevance of soil health indicators to the functions of wine grape soil health and establish benchmark values for these in dicators. A modified soil health assessment framework based on soil texture will be used in com mercial vineyards, focusing on the Stellenbosch region as a starting point. The results derived from this study can serve as a foundation for designing studies in other winegrape production areas to establish region-specific soil health assessment frameworks.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

WATER USE AND PERFORMANCE OF GRAPEVINE CULTIVARS IN RESPONSE TO CROP LOAD AND WATER REPLENISHMENT FROM THE SUBSOIL

SU-SS-J-MV 24-01 Mr John-Murray Visser, Department of Soil Science, Stellenbosch University Start date: 2024

AIM AND INDUSTRY RELEVANCE: Water scarcity challenges continue to be increasingly prominent, especially in wine-growing re gions. One way of addressing this challenge is by growing more drought-tolerant grape cultivars. As a result, a research project has been conducted since 2018 to evaluate the drought tolerance of a series of eight white and nine red cultivars. In this follow-up study, additional matters will be addressed, which include: • A comparison of the evapotranspiration of individual cultivars • How different crop loads affect cultivar performance • How the grapevines can ripen their crops while only using a fraction of one millimetre of water per day from January onwards. In this regard, two possible water sources will be investigated, namely: – Roots that explore the subsoil for available water – Water movement from the subsoil to the root zone through diffusivity Consequently, the main goal of the proposed project will be to assess the water usage and per formance of specific drought-tolerant cultivars as affected by crop load, root distribution, and water movement from the subsoil. The results will advise producers regarding differences in cultivar water use and crop load’s wa ter-saving, quality-enhancing and financial benefits. They will also clarify the role of the subsoil as a store for winter rain.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

EVALUATION OF ORGANIC FERTILISERS ON SOIL QUALITY AND WINE GRAPE PERFORMANCE

SU-SS AH 24-01 Prof Ailsa Hardie-Pieters, Department of Soil Science, Stellenbosch University Start date: 2024

AIM AND INDUSTRY RELEVANCE: Wineries experience consumer pressure to produce wines from vineyards using organic fertilisers, which are perceived to be more sustainable and environmentally friendly. Synchronising organic- or mineral fertiliser nutrient availability with crop uptake requirement is important to ensure high nutrient use efficiency and optimum crop production. In South Africa, there is a notable scarcity of local scientific data on how organic fertilisers impact the production of wine grapes. The extent to which organic fertilisers can provide the necessary quantities of mineralised nitrogen in sync with grapevine demand is not well known. This study aims to fill this knowledge gap by comprehensively evaluating and comparing major types of organic fertilisers to conventional ones and their impact on soil quality and winegrape production. To initiate this study, a comprehensive literature study will be conducted, whereafter a field trial is planned. The field trial will occur in a commercial 12-year-old Chardonnay vineyard grafted on Ramsey on a farm in Robertson. The different applications will be manually applied over three years. Each plot’s soil chemical and physical properties will be measured and identified before the commencement of the study. During the first year of the study, controlled laboratory mineralisation will be conducted to compare the C, N & P mineralisation dynamics of locally available organic fertilisers. The different treatments are as follows: • Control (no compost or fertiliser) • Commercial granular fertiliser applied after harvest, bud burst, and fruit set based on vine vigour (max 40kg/ha) • Blood-based organic fertiliser • Pelletised chicken manure organic fertiliser • Plant- & animal waste compost When all the data have been gathered, a financial evaluation will be conducted to ensure cost/ benefit figures support the vineyard’s performance.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

A MODEL VINEYARD IN POTS TO STUDY GRAPEVINE/SCION RESPONSES TO WATER LIMITATION

FShip Water 4 Prof Melané Vivier, South African Grape and Wine Research Institute, Stellenbosch University

Start date: 2023 Flagship Project

AIM AND INDUSTRY RELEVANCE: This research will aim to generate scenarios of water limitation on grapevines that can test the impact of the timing of and the severity of the water limitation, as well as the ability of the vines to adapt to the limitation and recuperate after successive drought scenarios. This project will provide a novel resource to the SA Wine Flagship Water Programme, namely a potted vineyard comprising a robust experimental design of 29 plant combinations (grafted and ungrafted vines), repeated nine times. It extends and draws on the other FShip Water projects (Fship 1-3) and will particularly support the ongoing research and showcasing of results obtained from Water Fship 3. The potted trial includes additional scion/rootstock combinations (grafted and ungrafted) not evaluated in FShip Water 3. With the vines planted in pots, a greater level of control can be achieved, a unique feature. When the plants experience water stress and to what level the stress will develop can be controlled. Any soil and geospatial variability are removed by using pots, and the genotype responses can be monitored with fewer confounding variables. More severe stress responses in a shorter period can be generated due to the limited soil volume, and rain can be excluded by covering the pots. Furthermore, the location and layout of the trial make it ideal for sensor and technology testing. This study will yield both academic outputs and practical information suitable to be transferred to the industry. The potted vines and the planned experiments will be ideal for showcasing the impacts of the modulated water limitations. The trial will serve as a demonstration site for indus try professionals and other stakeholders and where student engagement and training can occur.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

PRODUCING QUALITY GRAPES WITH LIMITED WATER

FShip Water 3 Prof Melané Vivier, South African Grape and Wine Research Institute, Stellenbosch University Project is co-funded by the Water Research Commission

Start date: 2022 Flagship Project

AIM AND INDUSTRY RELEVANCE: This study aims to evaluate and compare the adaptability and resilience of current commercial scion/rootstock combinations established and maintained under both optimal and sub-optimal water conditions using a holistic approach and novel techniques. The study’s main hypothesis is that grapevines (scions and rootstocks in combination) display adaptation to non-lethal water limiting conditions (through intrinsic and extrinsic factors) that can lead to their resilience to water stress conditions. From a practical point of view, this project intends to answer questions like “Can commercially planted scions/rootstocks adapt to much less water and still produce quality grapes?” and “What would be the critical aspects to consider towards such a goal?”. These seem like simple questions, but they cannot be answered without recognising the complex interaction of many factors that influence a vine’s success and resilience in a specific (natural or manipulated) environment. Therefore, they are currently largely unanswered. The Water Research Programme provided a model vineyard where grapevine water stress studies can be conducted over the lifespan of grapevines on a vineyard scale. This vineyard was designed (site selection, row layout and rootstock-scion selection) by the Water Programme Committee Workgroup and established in 2020 through a partnership between VinPro, Winetech and Stellenbosch University. The model vineyard will be a long-term resource to transfer knowledge and skills to the industry and viticulture students on the topic of grape production with limited water. It can showcase the outcomes of limiting water on a seasonal basis and over many seasons on a range of scion/rootstock combinations. The impact of innovative technologies in monitoring water stress could also be showcased.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

MEASURING THE EFFECT OF COVER CROPS ON SOIL AND VINE HEALTH, AND GRAPE QUALITY

EXPCo G32-22 Mr Daniel Viljoen, Experico, Stellenbosch Start date: 2023

AIM AND INDUSTRY RELEVANCE: This project aims to build on existing knowledge and investigate the effect of cover crop mixes on soil health and grapevines. With increased interest in more sustainable farming practices, more research is being done on using cover crops in agricultural systems. Local cover crop trials have recently been conducted in vineyards, focusing on cover crop mixes and their success, cover crop biomass and weed suppression. Using the right cover crop mix can increase soil moisture, improve soil structure, suppress weeds and pests, increase plant-available nutrients and improve crop resilience. This, in turn, reduces irrigation, pesticide, and fertiliser costs. In this project, the viability of growing cover crops under the vine and growing permanent cover crops will also be investigated. Analysis of nematode communities will add to the knowledge base of nematode host status of cover crop species. Care will be taken to include cover crops that will have a suppressive effect on inoculum and infestation levels of pathogens and/or pests. This project aims to provide the industry with crucial information to fill the knowledge gaps about selecting cover crops to improve the properties and ecology of soil in vineyards.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

DEMONSTRATION OF PLANT-BASED IRRIGATION ON WINE-GRAPE PERFORMANCE AND QUALITY IN THREE CLIMATICALLY DIFFERENT REGIONS FShip Water 2 Mr John-Murray Visser, Department of Soil Science, Stellenbosch University Project completed: 2023 Flagship Project AIM AND INDUSTRY RELEVANCE: Water scarcity is an escalating challenge for the agricultural sector, particularly in South Africa’s wine industry, where sustainable water use is critical for long-term viability. The project aimed to demonstrate the use of plant-based irrigation scheduling, specifically using stem water potential, as a practical and effective method to improve water use efficiency, grape quality, and vineyard sustainability across three climatically distinct wine-growing regions in South Africa. This approach is highly relevant in the context of increasing water scarcity and climate variability in South Africa, offering wine grape producers a science-based, adaptable strategy to manage irrigation more precisely by aligning water application with the actual needs of the vine. This study showed that plant-based irrigation scheduling, using stem water potential thresholds, can significantly reduce water use by up to 96% in some regions compared to the farmer standard practices, without compromising grape yield or quality. Water-stressed treatments often led to improved grape quality, including higher sugar content, greater flavour intensity, and more desirable wine composition. Sensory evaluations showed that wines produced under moderate stress (-1.5 MPa) were frequently rated higher in colour, taste, and aromatic complexity, especially in the Olifants River Valley. Additionally, the project evaluated remote sensing tools for irrigation planning purposes. Although helpful, these tools tended to overestimate crop water use, highlighting the need for plant-based validation to ensure accurate irrigation decisions. Overall, the results support precision irrigation as a sustainable solution for viticulture in water-limited environments and by implementing these strategies, growers can enhance water efficiency, reduce costs, and create a more sustainable future for their vineyards.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

SOIL HEALTH MANAGEMENT FOR SUSTAINABLE VITICULTURE: A FRAMEWORK FOR RESEARCH AND ON-FARM PRACTICE

SAGWRI ES 23-01 Prof Evodia Setati, South African Grape and Wine Research Institute,

Stellenbosch University Project completed: 2024

AIM AND INDUSTRY RELEVANCE: Soil health is essential for sustainable viticulture, directly affecting grapevine productivity, fruit quality, and the long-term viability of vineyards. This project aimed to identify key soil health indicators pertinent to viticulture and to develop a framework that guides sustainable soil man agement practices within the South African wine industry. Through a survey of 108 industry stakeholders and a literature review, the project evaluated current soil analysis practices and highlighted significant gaps, particularly in biological indicators. While chemical and physical parameters are well understood with established norms, biological indicators such as microbial activity and mycorrhizal colonisation lack standard benchmarks. Da ta-sharing constraints among producers hindered the development of a comprehensive database; however, the study successfully produced a reference framework outlining selected indicators and proposed guidelines for future practice. The results emphasise the urgent need for standardised, cost-effective biological assays and regional norms to support evidence-based decision-making in vineyard soil management. This work establishes the foundation for further research and industry collaboration in integrating biological indicators into routine soil health monitoring in viticulture.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

A NOVEL METHOD THAT TURNS WINE INDUSTRY EFFLUENT INTO VALUABLE PRODUCT STREAMS UWC BB 20-01 Prof Ben Bladergroen, South African Institute for Advanced Material Chemistry, Energy Storage and Fluid Treatment Centre, University of the Western Cape Project is co-funded by the Department of Science and Innovation Project completed: 2023 AIM AND INDUSTRY RELEVANCE: In this project, an unconventional, unprecedented, inventive, ground-breaking and robust technology will be tested on winery effluent. Previous research has shown it is a promising alternative to current available technology. Costs associated with both water consumption and waste water treatment form an ever increasing portion of the operational budget of many wineries, exacerbated by reduced rainfall and more stringent municipal regulations around effluent discharge. Re-use of winery wastewater for irrigation purposes without treatment is often not recommended as the Chemical Oxygen Demand (COD) and Total Dissolved Solids (TDS) levels cause the water to be an unfit source. The potential for water re-use in the wine industry is great but currently the cost of water treatment plants is too high, specifically for many small to medium scale wineries. This new technology address major shortcomings of current treatment systems and other challenges. These include cost efficiency of wastewater treatment and reducing the suspended solids, COD and TDS levels of effluent, making the treated effluent more compatible as a source for irrigation water.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

THE EFFECT OF DIFFERENT SCION/ROOTSTOCK COMBINATIONS ON GRAPEVINE WATER STATUS US SS EL1 Dr Vink Lategan, Department of Soil Science, Stellenbosch University Project completed: 2021

AIM AND INDUSTRY RELEVANCE: In a climate where water scarcity is an increasing challenge, especially in key wine-producing regions like the Western Cape, identifying cultivar-specific water stress thresholds is crucial for maintaining grapevine health, optimising yield, and ensuring consistent fruit quality. The primary aim of this project was to investigate the effects of different scion and rootstock combinations on grapevine water status under controlled environmental and soil conditions. The project established a pot trial of five red wine cultivars on four rootstocks to study water status responses under uniform conditions near Stellenbosch. Although challenges such as delays in the availability of plant material, infrastructure setbacks, and climatic disruptions limited the implementation of water stress treatments, the project successfully established the experimental system and collected valuable baseline data. Results showed clear variations in leaf water potential and vegetative growth among combinations, with the Ramsey rootstock often promoting stronger growth. A key outcome was the development of an affordable, Arduino-based soil moisture logging system, enhancing the feasibility of precision irrigation monitoring. These findings provide foundational insights into grapevine water relations and support future research aimed at improving irrigation scheduling and sustainable vineyard management.

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2. VITICULTURE RESEARCH NEW PROJECT

2.4 CULTIVATION ReGenWine (ReGEN)

SAGWRI MAV 25-01 Mrs Julia Harper, Faculty of AgriSciences, Stellenbosch University Start date: 2025

AIM AND INDUSTRY RELEVANCE: Producers should consider diversification strategies to address climate change, rising production costs, and the increasing demand for sustainably produced wine. ReGEN advocates for a shift to regenerative practices to address these challenges. However, wine farmers require scientific validation that regenerative farming systems can sustain wine quality and production long-term and that the benefits justify the investment costs involved. The project aims to address the viability of transitioning from conventional farming practices to a more regenerative approach, while also quantifying the long-term benefits to the soil, plants (cover crop and vine) and quality of wine. A pre-trial with a multidisciplinary project team will be conducted on a commercial farm to evaluate the benefits of regenerative practices for the soil, plants, animals and wine production. This will allow for a thorough evaluation of regenerative agricultural practices over time. The project will assess the following based on the key principles of regenerative agriculture: • Evaluate the impact of adopting the five principles of regenerative practices on soil health, soil microbiome, vine development, grape and wine quality, and compare the economic sustainability of these practices to conventional farming. • Develop a better comprehension of how regenerative agriculture can support the creation of a circular economy within vineyards. • Distinguish emerging regenerative practices that can be tested and potentially be applied by the wine industry.

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SOUTH AFRICA WINE RESEARCH 2025

2. VITICULTURE RESEARCH PROJECT IN PROGRESS

ANALYSING INDUCED DIVERSITY IN A COLLECTION OF PINOTAGE PLANTS AFTER GAMMA IRRADIANCE P04000060-2024 Prof Melané Vivier, South African Grape and Wine Research Institute, Stellenbosch University and Ms Phyllis Burger, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC-Infruitec-Nievoorbij Start date: 2024 AIM AND INDUSTRY RELEVANCE: Pinotage has only a few commercially available clones similar in viticultural and oenological properties. This project builds on the previous work done in 2017 and 2018 (optimised methodology to establish a gamma-irradiated Pinotage collection) and from 2019 until 2023 (irradiated Pinotage collection initially characterised). This project aims to expand upon these prior research efforts and perform viticultural and oenological assessments on selected groups of vines. This aims to pinpoint promising candidates for the clonal selection of Pinotage. The objectives for this project are as follows: • Develop a data management plan for the project. • Maintain and extend the field site where an irradiated population of Pinotage plants are kept. • Investigate the effects of gamma irradiance on the cluster, canopy, and wine quality traits of three Pinotage clones in a field trial site. • Select promising individuals for grafting to rootstocks for further analyses.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

IN-FIELD QUANTIFICATION OF GRAPEVINE KEY ANALYTES USING PORTABLE INFRARED SPECTROSCOPY DEVICES

SAGWRI JT 24-01 Dr Jose Luis Aleixandre-Tudo, South African Grape and Wine Research Institute, Stellenbosch University Start date: 2024

AIM AND INDUSTRY RELEVANCE: Knowledge of key analyte levels in the grapevine growing season is hindered by analytical limitations such as time-consuming protocols, expensive analytical procedures, and limitations of the technology for direct measurement in grapevine tissue. Furthermore, spectroscopy calibrations are not optimised for in-field conditions. This project aims to supply optimised prediction calibrations for in-field direct quantification of important analytes from grapevine organs, such as shoots, leaves and berries. The target analytes are carbohydrates, nitrogen and amino acids. Ambient variability will also be incorporated into the models to optimise prediction accuracies. The Chenin blanc vineyard, which is part of the research project “Premium and profitable Chenin blanc wines,” and the Flagship Project 3 vineyard will be the sources used to acquire the required variability for calibration optimisation. Three different experiments will be conducted under this objective. • The Flagship Project 3 vineyard’s nutrient content will be monitored and assessed during a growing season using optimised calibrations. • Amino acid development will be monitored in the Chenin blanc experimental vineyard during grape ripening. • Lastly, the effect of the nutrient content on the take percentage of grafting material will be assessed. In this instance, a sample set containing materials with varying nutrient content levels will be utilised to demonstrate the concept. If successful, the project’s outcome will benefit the nursery industry’s supply chain due to the potential optimisation of plant material. Overall, it will improve the quality of the plant material, grapevine development and grape and wine quality.

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SOUTH AFRICA WINE RESEARCH 2025

2. VITICULTURE RESEARCH PROJECT IN PROGRESS

THE MAINTENANCE AND EXPANSION OF A GENETIC SOURCE FOR VINES

P04000068 Ms Phyllis Burger, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC Infruitec-Nietvoorbij Ongoing

AIM AND INDUSTRY RELEVANCE: This project is responsible for the maintenance and expansion of the South African national grape genebank. It involves: • Maintaining field genebanks and a backup repository; • Importing of promising cultivars for wine making and breeding purposes; • Adding newly imported accessions and new locally bred accessions to the genebank; • Supplying plant material to local Plant Improvement Organisations and to institutions abroad on request; • Propagating backup plants of accessions that are dying in field genebanks; • Ampelographical description of cultivars for authentication; • DNA fingerprinting of accessions in the genebank; • Viticultural and oenological evaluation of promising wine grape cultivars.

SOUTH AFRICA WINE RESEARCH 2025

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2. VITICULTURE RESEARCH NEW PROJECT

2.5 TERROIR

ESTABLISHMENT OF THE TECHNICAL AND SCIENTIFIC BASES FOR AI APPLICATIONS IN WINE PRODUCTION: STUDY CASE ON VITICULTURE, YIELD AND PHENOLOGY AI MODELS SAGWRI CP 25-01 Prof Carlos Poblete-Echeverria, South African Grape and Wine Research Institute, Stellenbosch University Start date: 2025 AIM AND INDUSTRY RELEVANCE: Human field scouting has long been used to monitor various vineyard processes and practices. However, this approach is expensive, labour-intensive, subjective and often lacks precision. New methods to assess vine performance that move beyond traditional practices are needed. Artificial intelligence (AI) offers a groundbreaking and powerful technological tool to enhance and improve present monitoring methodologies and data management processes. Designing AI algorithms with fast and proficient learning tempo, quick convergence to solutions, effective abstraction skills and ease of implementation are essential to developing a successful and effective AI model. The project aims to lay the technical and scientific groundwork for implementing AI applications in the South African wine industry by building both human and technological capabilities necessary for these models. A case study on yield and phenology will be the focus point for establishing the core principles. In addition, these principles can be applied to other AI applications in both Viticulture and Oenology.

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SOUTH AFRICA WINE RESEARCH 2025

2. VITICULTURE RESEARCH PROJECT IN PROGRESS

GENERATING HIGH RESOLUTION, VINE-SPECIFIC ACTUAL EVAPOTRANSPIRATION MAPS AT DAILY INTERVALS

SU-GEO TS 24-01 Dr Tara Southey, Department of Geography & Environmental Studies, Stellenbosch University Start date: 2024

AIM AND INDUSTRY RELEVANCE: Due to population and economic growth, climate change and the decline in water quality, South Africa faces water scarcity challenges. Accurate estimates of crop water demand through evapotranspiration (ET) modelling are increasingly important to improve irrigation management and maximise water use efficiency. This study aims to develop and demonstrate a methodology for generating high-resolution (10 m), daily, grapevine-specific, actual ET maps. The project has a six-phase work plan approach. 1. Review methods, algorithms and data sources for calculating actual ET (Eta). 2. Hourly Et0 values will be calculated for each weather station point. 3. Images from Sentinel-2 will be sourced and compared to existing crop coefficient (Kc) values using regression analysis. 4. The best-performing vegetation index-based Kc model from Workplan 3 will be combined with the Et0 surfaces from Workplan 2. 5. Inter-row areas with established cover crops (or dense weed populations) can significantly affect the growth and vigour signals received from the satellite. An attempt will be made to quantify this effect by comparing indices derived from 10 m resolution images to those derived from 50 cm resolution images. 6. Using in-field observations by an expert panel, the Eta surfaces from Workplan 4 will be evaluated at key grapevine growth stages and in response to irrigation and/or rainfall events. The project’s final phase involves engaging with industry role players to investigate the potential of integrating the developed method with existing irrigation scheduling tools and determine the appetite for offering ET0 and ETa maps through TerraClim.

SOUTH AFRICA WINE RESEARCH 2025

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

CLIMATE DATABASE AND TERRACLIM TOOL DEVELOPMENT

FShip TerraClim 2022 Dr Tara Southey, Department of Geography & Environmental Studies, Stellenbosch University Project is co-funded by the Department of Science and Innovation

Start date: 2022 Flagship Project

AIM AND INDUSTRY RELEVANCE: This project continues to build on the Terraclim project that started in 2019. The initial TerraClim project has provided an excellent foundation for research. The online Terraclim platform (www.terraclim.co.za) is a new, integrated technology tailored to the agriculture sector. It is ideal for aiding long and short-term decision-making at the farm and field level in the context of climate change in the complex terrain of the Western Cape. Terraclim provides high-resolution terrain and temperature information based on a robust climate and terrain database. The project will maintain, extend and improve the climate database and wireless logger networks. However, the initial TerraClim project also generated a wealth of data that has not yet been exploited. This new project aims to mine the geospatial database (geodatabase) for information related to climate variability and cultivar suitability. This research aims to answer the ultimate question of what actions are required to ensure a sustainable future for the wine industry. However, to answer this question, we first need to improve our understanding of climatic variations of the recent past so that we can identify trends and make predictions of how variations may play out in the near- and long-term future. With this background, we can potentially improve our understanding of how climate change may affect the wine industry, especially within the context of what has happened in the wine industry over the past few years. The continuation of the Terraclim project builds on the previous aim to improve our understanding of how the climate in the Western Cape is changing and how the grapevine/plant is responding to these changes. This knowledge is critical for the sustainable future of wine production in South Africa. This project will ultimately: 1) provide up-to-date climate situational reports for within-season decision-making 2) delineate areas most at risk of climate variability to inform new plantings 3) map terroir to understand wine character better 4) identify areas most suitable for the planting of specific cultivars 5) maintain and expand the centralised climate database.

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SOUTH AFRICA WINE RESEARCH 2025

2. VITICULTURE RESEARCH PROJECT IN PROGRESS

ASSESSING THE DROUGHT TOLERANCE OF SELECTED GRAPEVINE SCION CULTIVARS UNDER DRYLAND CONDITIONS IN THE SWARTLAND REGION

P04000207 Dr Carolyn Howell, ARC Infruitec-Nietvoorbij, Stellenbosch Project is co-funded by the ARC Infruitec-Nietvoorbij Start date: 2018

AIM AND INDUSTRY RELEVANCE: The objective of the project is to determine the drought tolerance of selected alternative scion cultivars in comparison to reference cultivars. According to climate change forecasts, rainfall in the Western Cape could become lower over time. Drought tolerance refers to the degree to which a plant is adapted to arid or drought conditions. Drought tolerant scion cultivars could ensure more sustainable viticulture in the dryland and irrigated regions in the Western Cape, or if climate change results in reduced rainfall. A number of drought tolerant scion cultivars, not currently extensively planted in South Africa but that could hold promise for the wine industry, have been identified. However, there is presently no scientifically based information regarding the growth, yield and quality aspects for the recommended alternative scion cultivars under South African conditions. This project aims to generate the knowledge to make recommendations on scientifically verified results. A new vineyard will be established, with 17 different scion cultivars. It must be noted that the project aims to assess grapevine responses in an almost worst case scenario, i.e. under dryland conditions in a sandy soil in the Swartland region. This will enable extrapolation of the findings to other soil-climate scenarios.

SOUTH AFRICA WINE RESEARCH 2025

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

2.6 GRAPEVINE IMPROVEMENT SELECTION OF GLRaV-3 RESISTANT ROOTSTOCKS FOR THE SOUTH AFRICAN WINE INDUSTRY

PATHSOL GP 24-01 Prof Gerhard Pietersen, Patho Solutions Start date: 2024

AIM AND INDUSTRY RELEVANCE: Grapevine Leafroll-associated Virus 3 (GLRaV-3) can be transmitted to vines during the grafting process via GLRaV-3-contaminated rootstocks. It has been demonstrated that GLRaV-3 susceptible and resistant individuals exist within the Vitis rootstock selection most frequently used in South Africa. This study aims to select GLRaV-3-resistant rootstocks of the six most vital rootstock cultivars, establish them, verify their resistance, and make them widely available to the industry. The process will start with identifying sources of potentially resistant rootstocks and then selecting GLRaV-3-resistant individuals of rootstocks 101-14 Mgt, Paulsen 1103, Richter 99, Richter 110, Ruggeri 140 and US 8-7. Additional testing will ensure no other pathogens are found in these individuals, followed by establishing resistant rootstock sources in a vector-free environment. Further confirmation of the absence of GLRaV-3 will be done, followed by GLRaV-3 resistance confirmation via artificial inoculation, in which pure sources of GLRaV-3 variants will be grafted onto young plantlets from each source of the selected rootstock. The last step will be distributing the selected immune phenotype material to plant improvement organisations within the South African wine industry.

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SOUTH AFRICA WINE RESEARCH 2025