Grapevine quality from vineyard to shelf: Response of Crimson Seedless and Italia to meso-climate, water regime and ripeness level

PROJECT TITLE:    Grape quality from vineyard to shelf: Responses of Crimson Seedless and Italia to mesoclimate, water regime and ripeness level

Project leader:           Janéne Strydom/Kobus Hunter (ARC Infruitec-Nietvoorbij)

Contact:                     strydomj@arc.agric.za

Duration:                    1 April 2020 to 31 March 2023

Problem identification and project objectives:

The table grape industry is a highly advanced and progressive global entity with strictly regulated international standards. Table grapes are recognised as a healthy agricultural produce and the export thereof is an economic priority on the highly competitive international markets.

It has become increasingly difficult to maintain acceptable and competitive standards under Mediterranean conditions with limited water availability for agricultural use and additional pressure from changes in climatic patterns. To remain competitive and to maintain markets and to expand to new markets, industries all over the world require constant technological advancement. Such technological advancement requires a deep understanding of grapevine reactions. However, limited scientific information on the morphological, chemical and pathological status of table grapes along the whole value chain from vineyard to shelf hinders the understanding of grapevine reactions. Thus, efficient regulatory management of the condition and status of table grapes in response to abiotic factors also is hindered.

This situation created by the limited available scientific information is exasperated by the current pressure on water resources for agricultural use, due to inter alia urbanisation and climate change. This is further complicated by a table grape cultivation practice scenario in which many different products/stimulants are standardly applied to improve growth balances as well as the appearance and eating and keeping quality of grapes. Biochemical and physiological processes may be affected and complicate the understanding of plant behaviour with the objective to control growth balances and berry quality.

In order to facilitate the control of vegetative and reproductive growth variables that determine yields, ripening conditions, as well as grape quality at harvest and during storage, table grapes are intensively irrigated and are therefore highly dependent on water resources. An absence of proper water supply during grape development would result in unacceptable, small berry sizes and too low yields available for local and international distribution. This would seriously affect sustainability of produce, with further implications at socio-economic levels. These circumstances create a very complex scenario in which table grape yields and quality must be maintained and preferably increased while, at the same time, the global drive for competitiveness must be satisfied.

The climatic conditions at macro-, meso- and microclimate levels are extremely important in the management of growth, disease control and grape quality parameters in the vineyard. These, meso- and microclimate conditions are to a large extent controllable by producers by means of e.g. row orientation, trellis system, row and vine spacing, netting, and plastic covering. By changing the mesoclimate, plant behaviour can be affected favourably in different environments. It provides a means to buffer the vineyard or even stabilise vineyard conditions during erratic seasonal weather and at a larger scale against climate change related patterns of high temperature and drought. However, the effect of altered mesoclimates is not sufficiently explored under South African conditions.

A deep understanding of plant reaction at morphological and physiological levels to water supply (and climatic conditions) is required, whereas grape quality parameters would need to be investigated at a much higher level than the current basic indicators to maintain a sustainable product and to stay at the forefront of technology in a very challenging agricultural scenario.

Climate is central in regulatory management and environmental changes, mesoclimate, water supply, as well as cultivation practices affect grapevine phenology, yields, grape quality, and grape storage ability. Grapevine responses due to the combined effects of climate and cultivation practices are related to physiological and morphological processes but are complicated to understand. This requires thorough investigation.

This project aims: 1) To determine the impact of different water regimes and an altered mesoclimate (obtained by comparing open field conditions with complete covering of a vineyard with plastic), combined with standard cultivation practices and bunch manipulation techniques (thinning, sizing), on vegetative and reproductive growth; 2) To determine the relationship between water regimes, meso-climatic conditions, and grape primary and secondary quality compounds along the whole value chain from vineyard to shelf.