South Africa Wine Research Projects

PROJECTS 2024 RESEARCH

RESEARCH, DEVELOPMENT AND INNOVATION

www.sawine.co.za

TABLE OF CONTENTS

1 FOREWORD ____________________________________________2

2 VITICULTURE RESEARCH __________________________________4 2.1 Grapevine protection – Insects and pests _ __________________6 2.2 Grapevine protection – Fungi and bacteria ___________________8 2.3 Soil and water _______________________________________ 14 2.4 Cultivation __________________________________________ 24 2.5 Terroir _____________________________________________ 27 2.6 Grapevine improvement _ ______________________________ 30

3 OENOLOGY RESEARCH _ ________________________________ 44 3.1 Wine improvement _ __________________________________ 46

4 TECHNOLOGY TRANSFER ________________________________ 59

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1 FOREWORD

The South African wine industry stands at a moment in its history when innovation, sustainability, and adaptability are more important than ever. With an increasingly complex global market driven by evolving Environmental, Social, and Governance (ESG) reporting standards, it becomes essential to address and overcome our industry’s most pressing challenges. South Africa Wine has dedicated itself to this cause, developing and implementing various strategies to ensure our wine industry’s economic viability and market growth. The South Africa Wine Research, Development, and Innovation (RDI) strategy is central to these efforts. This strategy underscores our commitment to funding academic research projects that span vineyard management, pest and disease control, grape and wine quality improvement, climate change adaptation, water efficiency, soil health, and sustainable production practices. Through close collaboration with industry stakeholders, including wine producers, winemakers, researchers, and academic institutions, we aim to facilitate sustainable grape and wine production, delivering quality wines that can be marketed and sold profitably.

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Our strategic objectives encompass flagship programmes, the generation of scientific knowledge relevant to both industry and academia, innovation and research business ventures, the development of a South African wine blockchain ecosystem, the formulation of a holistic sustainability strategy (ESG Roadmap), knowledge transfer, industry engagement, and international partnerships. The flagship programmes are particularly noteworthy. These large-scale, strategically focused, and ambitious initiatives address the multifaceted challenges of climate change, water efficiency, plant breeding, and wine authenticity. By integrating individual projects into comprehensive programmes, we strive to push the boundaries of knowledge production and innovation, exploring groundbreaking ideas, methodologies, and technologies. This book is a testament to our ongoing efforts. It offers a detailed compilation of summaries of research projects concluded by the end of 2023 and those currently underway in 2024. Organised according to the specialised committees overseeing them, this book aims to create awareness of the research initiatives funded by South Africa Wine and acknowledge the dedication and hard work of the researchers leading these projects. We hope this collection will inspire continued collaboration, innovation, and progress within the South African wine industry, ensuring stakeholders’ sustainable and prosperous future.

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) DR KARIEN O’KENNEDY: Knowledge Transfer Manager (karien@sawine.co.za)

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2 VITICULTURE RESEARCH

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

2.1 GRAPEVINE PROTECTION – INSECTS AND PESTS 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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2.2 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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DETERMINING FACTORS THAT MAY REDUCE/SHORTEN THE PRODUCTIVE LIFESPAN OF ROOTSTOCK MOTHER PLANTATIONS

P04000235 Prof Francois Halleen, ARC Infruitec-Nietvoorbij, Stellenbosch Project was co-funded by the ARC Infruitec-Nietvoorbij Project completed: 2023

AIM AND INDUSTRY RELEVANCE: The Vine Improvement Scheme provides multiple requirements, but none address the productive lifespan of rootstock mother blocks. This study aimed to simultaneously determine the incidence of trunk disease pathogens, - physiological status, and morphological dimensions of rootstock canes across mother blocks of different ages to manage and plan for the replacement thereof. A survey was conducted in a selection of mother blocks to assess these aspects across three seasons and to evaluate the occurrence of trunk pathogens of vine heads in mother blocks over two seasons. The impact of infection on callus formation and performance of nursery vines was also investigated. Important grapevine trunk disease pathogens were identified in the mother blocks’ vine heads and canes, which pose certain challenges during propagation or in newly established vineyards. The results show that one-year-old canes serve as an inoculum source in newly grafted vines. They are also responsible for shortening the lifespan and compromising the capacity of mother blocks to yield healthy canes. The morphological and physiological data from the one-year-old canes were influenced by season and not by rootstock mother vine age, but total pathogen incidences increased with vine age. It is, therefore, of the utmost importance that grapevine trunk diseases in rootstock mother blocks be managed more effectively and replacement planning done at a younger age.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

EFFECT OF MECHANICAL PRUNING ON GRAPEVINE TRUNK DISEASES

P04000236 Prof Francois Halleen, ARC Infruitec-Nietvoorbij, Stellenbosch Project was co-funded by the ARC Infruitec-Nietvoorbij Project completed: 2023

AIM AND INDUSTRY RELEVANCE: This study aimed to investigate the effect of mechanical pruning (MP) on the presence of grape vine trunk disease pathogens in contrast to conventional hand pruning (HP). Selected vineyards were hand- or mechanically pruned during four consecutive dormant seasons. To assess pathogen occurrence and severity, fungal isolations were done on pruning wounds and older three to four weeks post pruning. Overall, HP vines exhibited a higher occurrence and severities of dieback and canker pathogens compared to MP vines, with the differences primarily stemming from larger cuts made close to the cordon in HP vines. Therefore, do not make large cuts close to the cordon. In addition, MP vines featured longer canes, providing increased opportunities for the vine to counterpoise dying shoots. The researchers concluded that mechanical pruning in a single (MP1) or double cordon (MP3) and using hand pruning using shears and a mechanical saw that mimicked a mechanical pruning method (MP3) appears to be a viable option of pruning resulting in less than expected trunk pathogen infections.

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2. VITICULTURE RESEARCH NEW PROJECT

2.3 SOIL AND WATER

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 NEW PROJECT

EVALUATION OF ORGANIC FERTILISERS ON SOIL QUALITY AND WINE GRAPE PERFORMANCE

SU-SS AH 24-01 Dr 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

DEMONSTRATION OF PLANT-BASED IRRIGATION ON WINE-GRAPE PERFORMANCE AND QUALITY IN THREE CLIMATICALLY DIFFERENT REGIONS

FShip Water 2 Dr Vink Lategan, Department of Soil Science, Stellenbosch University

Start date: 2019 Flagship Project

AIM AND INDUSTRY RELEVANCE: Previous research has shown that wine grapes need 250 to 350 mm irrigation water for optimum yield. However, this was primarily determined for vineyards in the coastal region under normal winter and spring rainfall conditions. Consequently, it needs to be established if these irrigation amounts will be sufficient in the warmer, drier grape growing regions, and if not, to what extent they should be adjusted. The objective of this study is to develop guidelines based on grapevine water status for wine grape irrigation. In order to apply the minimum irrigation requirement, sound irrigation scheduling practices are essential. This project will be conducted in the form of demo plots in established commercial vineyards, in three climatically different areas (Stellenbosch, Breedekloof and Olifants River). Irrigation scheduling will be done based on plant water potential values based on previous research and compared to the grower’s normal scheduling practice. The effect of the treatments on vegetative parameters, yield and water use efficiency will be evaluated. Since this project will be carried out in a number of vineyards, it is an ideal opportunity to validate remote sensing systems, e.g. satellite or drone images, for application in a variety of commercial vineyards. Experimental wines will also be made and evaluated while economic factors will also be considered. The knowledge on grape and wine responses will empower growers to save irrigation water while obtaining the best wine quality and maximum profit.

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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 Dr Annika Pienaar, 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 PROJECT IN PROGRESS

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 Start date: 2023

AIM AND INDUSTRY RELEVANCE: This project aims to identify key soil health indicators and threshold values to generate guidelines on best practices for analysing soil health in South African viticulture and draft a report highlighting common soil health indicators relevant to the wine industry and a Soil Health Research framework to aid producers with decision-making around soil health interventions. In viticulture, healthy soil is crucial to support grapevine growth and the production of good-quality grapes. For this purpose, the soil must have balanced physical, chemical and biological attributes. To assess this, regular testing is conducted. A suite of physical, chemical and biological indicators is measured and interpreted against known threshold values. However, critical soil values for some biological indicators were adapted from orchards and therefore are not specific to grapevines. Furthermore, biological indicators, such as soil microbial biomass, measure the total size of the microbial population but not its composition or functional potential. Consequently, existing criteria and guidelines for interpreting soil health assessment data and how to best use the outcomes to sustain economically feasible and effective grape production do not always adequately facilitate decision-making. Existing threshold values can be refined to generate more viticulture realistic target values. Several outputs will be generated from the study. These include: A draft framework for soil health research and measurement in viticulture and wine production An infographic will be created to be used as a reference tool for soil health and with other tools for training workshops or webinars.

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2. VITICULTURE RESEARCH PROJECT IN PROGRESS

A NOVEL METHOD THAT TURNS WINE INDUSTRY EFFLUENT INTO VALUABLE PRODUCT STREAMS

UWC BB 20-01 Prof Ben Bladergroen, South African Institute for Advanced Materials Chemistry Energy

Storage and Fluid Treatment Centre, University of the Western Cape Project is co-funded by the Department of Science and Innovation Start date: 2020

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 aims to 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 PROJECT IN PROGRESS

THE EFFECT OF DIFFERENT SCION/ROOTSTOCK COMBINATIONS ON GRAPEVINE WATER STATUS US SS EL1 Dr Vink Lategan, Department of Soil Science, Stellenbosch University Start date: 2016

AIM AND INDUSTRY RELEVANCE: The main aim of this trial is to investigate how different cultivar scion and rootstock combinations affect plant water potential, under similar climatic conditions, soil type and water status. Both grapevine scion cultivars and rootstock varieties differ in their tolerance and response to limited water supplies. The reaction of a grafted vine to water stress cannot necessarily be predicted from the scion and rootstock varieties’ individual reactions. Information gained from this research would help to adapt published plant water potential thresholds for more accurate irrigation scheduling to improve fruit and wine quality. A number of different scion and rootstock cultivars, in different combinations, have been selected for this trial which will be an experiment conducted in pots. Water usage of different scion/rootstock combinations as well as plant vegetative and reproductive responses under different irrigation regimes will be evaluated.

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2. VITICULTURE RESEARCH COMPLETED PROJECT

GRAPEVINE’S RESPONSE TO WATER STRESS USING DIFFERENT SCION/ROOTSTOCK COMBINATIONS

IWBT 18-01 Prof Melané Vivier, South African Grape and Wine Research Institute,

Stellenbosch University Project completed: 2023

AIM AND INDUSTRY RELEVANCE: Grapevine scion cultivars, as well as rootstocks, display different levels of tolerance to water stress. This project aimed to assess grapevine response(s) to water deficit stress at molecular and physiological levels in potted vines via computational analysis to identify biomarkers in grapevines. Quantification of transcriptional responses to water stress and various devices and sensors were assessed for their sensitivity and precision in monitoring grapevine responses to water stress alongside established reference techniques. The study confirmed that the grapevine’s response to water stress is intricate and is influenced by the timing and severity of stress and genotype. Genotype differences in rootstock and scion responses were evident. The grapevines exhibited high adaptability, with acclimation appearing to be a crucial mechanism employed by grapevines in response to recurring stress events. It was found that young vines showed varied responses to stress that lessen with maturity. Molecular markers were verified to be working to respond to water stress. The potted vines provided an optimal environment for active drying experiments, and the population thereof will serve as an asset to educate, train and study water stress in grapevines using active drying experiments, molecular markers and sensor technology. Future work that expands on these results will inform vineyard management tools like cultivar and rootstock selection as an adaptation strategy.

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2. VITICULTURE RESEARCH NEW PROJECT

2.4 CULTIVATION 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 NEW PROJECT

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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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 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.

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2. VITICULTURE RESEARCH NEW PROJECT

2.5 TERROIR

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.

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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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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 2024

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2. VITICULTURE RESEARCH NEW PROJECT

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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2. VITICULTURE RESEARCH NEW PROJECT

ESTABLISHMENT OF GRAPEVINE LEAFROLL ASSOCIATED VIRUS 1 AND 2 ELISAS

PATHSOL GP 24-02 Prof Gerhard Pietersen, Patho Solutions Project is co-funded by Patho Solutions Start date: 2024

AIM AND INDUSTRY RELEVANCE: Grapevine Leafroll-associated Virus-3 (GLRaV-3) is the most widespread and the focus of control of leafroll-associated viruses. Other associated viruses like GLRaV-1 and -2 also occur; however, only GLRaV-3 ELISA tests are available, so there is a need for ELISAs for GLRaV-1 and -2. The Vine Improvement Association (VIA) certification scheme mandates GLRaV-1, -2, and -3 tests. In the past, this was done via a locally prepared single ELISA system that could detect these three viruses. This test, however, is no longer available, and currently, only GLRaV-3 testing is locally available and affordable. This project aims to develop ELISA tests to detect GLRaV-1 and GLRaV-2 and, if successful, combine them into a GLRaV1, -2, & -3 cocktail ELISA, which can detect all three viruses within a single test.

SOUTH AFRICA WINE RESEARCH 2024

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2. VITICULTURE RESEARCH NEW PROJECT

GENOMIC COMPARISON OF RAMSEY GLRaV-3 IMMUNE AND SUSCEPTIBLE SOURCES

PATHSOL GP 24-03 Prof Gerhard Pietersen, Patho Solutions Project is co-funded by SF & VR du Toit Studiefondstrust Start date: 2024

AIM AND INDUSTRY RELEVANCE: Recent, ongoing research has revealed GLRaV-3 susceptible, tolerant and immune phenotypes in Ramsey ( Vitis champinii ) sources. The reason for these differences is unknown. This project aims to compare the genomes of the different phenotypes on a molecular level in an attempt to find the underlying cause. A detailed genetic and genomic comparison between resistant and susceptible near-isogenic Ramsey individuals may lead to identifying the potential gene(s) underlying the resistance. This knowledge creates the possibility of incorporating leafroll resistance into not only other rootstocks but also into scions and to understand the virus’s mode of infection better. Vitis champinii is also a recognised stress-tolerant Vitis species, and the characterisation of its genome will also be of value in endeavours to identify further drought-tolerant vines. The project has five objectives: • Identify near-isogenic Ramsey material that shows a range of resistance to leafroll - susceptible, tolerant and immune. • Perform phased diploid genome sequencing on immune and susceptible material. • Assemble diploid genomes of the immune and susceptible clones. • Perform transcriptome analysis on immune and susceptible clones. • Screen assembled genome data and transcriptome data for functional sequence variations potentially underlying the resistance/susceptibility trait. The project has received support and positive feedback from industry organisations and wineries, highlighting the importance of finding solutions to combat the leafroll virus in the wine industry.

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