Researcher: Prof Melané Vivier, South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University
Aim and industry relevance:
One of the goals of the Water Programme was to design a research and showcasing study where several cultivars and rootstocks will be compared for their reaction and potential adaptation to reduced availability of water. These activities will be covered in the Water Flagship3 project. Innovative monitoring tools derived from the current Water Flagship1 will be incorporated and showcased to implement more effective monitoring/managing of plant water stress.
One approach currently ongoing as part of the Water programme is demonstration blocks at different commercial sites to showcase the vineyard level responses when water is limited to below industry norms (Water Flagship2 project). Although this showcases the effect of reduced water on production parameters at those sites, it does not provide explanations for what is observed, making generalisation to other sites, seasons, and cultivars impossible.
With climate change impacts becoming evident, consistent water scarcity is a long-term threat to grapevine production, particularly in the water-scarce South Africa. Breeding programs for more drought resistant vines remain an international priority, but in the short-to-medium term, we must assume that current commercial scions/rootstocks will remain the mainstay of the local industry. Much research has been gathered regarding the management of water regimes towards optimal production and product quality, but the assumption in most of these studies has always been, when needed, enough water would be available to the plants (through irrigation or rainfall). Despite the excellent local work that is informing the current best water management/irrigation practices, it is important to prepare our industry for scenarios where our portfolio of vines, planted in the current vine-growing areas will be consistently/periodically under severe water limitations.
This study, therefore, 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 main hypothesis of the study 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 is intended to provide answers to 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 a multitude of factors that influence the success and resilience of a vine in a specific (natural or manipulated) environment and therefore they are currently largely unanswered.
The Winetech Water Research Programme made provision for 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 as well as rootstock-scion selection) by the Water Programme Committee Work group 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 to viticulture students on the topic of grape production with limited water. It provides the ability to showcase the outcomes of limiting water on a seasonal basis, but also over many seasons on a range of scion/rootstock combinations. The impact of innovative technologies in monitoring for water stress could also be showcased.
Image credit: T Venter