The use of local knowledge relating to vineyard performance to identify viticultural terroirs in Stellenbosch and surrounds

Climate is a key variable for grapevine development and berry ripening processes. At mesoscale level, climate spatial variations are often determined empirically, as weather station networks are generally not dense enough to account for local climate variations.

Conventional molecular analyses provide bulk genomic/transcriptomic data that are unable to reveal the cellular heterogeneity and to precisely define how gene networks orchestrate organ development. We will profile gene expression and identify open chromatin regions at the individual cells level, allowing to define cell-type specific regulatory elements, developmental trajectories and transcriptional networks orchestrating organ development and function. We will perform scRNA-seq and snATAC-seq on leaf/berry protoplasts and nuclei and combine them with the leaf/berry bulk tissues obtained results, where the analysis of transcripts, chromatin accessibility, histone modification and transcription factor binding sites showed that a large fraction of phenotypic variation appears to be determined by regulatory rather than coding variation and that many variants have an organ-specific effect.

In 2020 one out of  eight wine bottles were filled with a flavoured wine-based beverage.

Smoke impacts on wines are becoming a worldwide problem; the size and severity of wildfires increasing due to influences from changing climates.¹ For over a century, wines have been known to have a unique issue of absorbing chemical compounds derived from wildfire smoke wherein the flavor of the subsequent wine becomes ashy, rubbery, campfire-like, and smoky.² The economic impacts of a smoke-impacted wine can last for years depending on the grape varietal, costing Oregon and Washington states in the United States over a billion dollars from the 2020 wildfires, as an example.³ While years of research have indicated elevated concentrations of smoke-related compounds, such as guaiacol and syringol, in wines after smoke events, unfortunately, replicating the sensory experience using smoke-associated phenols has not had much success.⁴

The increasingly frequent heat waves during grape ripening pose challenges for high quality wine grape production. Defoliation is a common practice that can improve the control of diseases in bunches, but also it increases the exposure to sunlight. Grapes exposed to solar radiation reach temperatures over the optimum for berry development and maturation. This makes the development of irrigation and canopy management techniques of great importance to maximize yield and grape quality. A field experiment was carried out during 2021 using Manto negro wine grapes to study the effect of applied irrigation and different light exposure levels on grape quality. Two irrigation treatments were imposed based on the frequency and amount of water doses in a four-block experimental vineyard at Bodega Ribas (Mallorca). Three light exposure treatments were randomly applied in each irrigation plot. The light treatments included exposed clusters from pea size, non-exposed clusters, and shaded clusters after softening. Leaf area index and canopy porosity was estimated every 2 weeks. Midday leaf water potential was measured weekly. Additionally, apparent electrical conductivity was measured between rows to estimate the soil water content variability. Light and temperature sensors were installed at the bunch level to quantify the differences in bunch temperature and light intensity among treatments. The effect of irrigation and cluster light exposure on berry weight, TSS, TA, malic acid, tartaric acid, K+, and pH were analysed at 5 moments along grape ripening. During different heat waves, the natural shading technique decreased the maximum bunch temperature around 10 °C respect to the exposed bunches in both irrigation strategies. The combination of defoliation and shading techniques after softening decreased TSS at harvest and affected most of the quality parameters during the last stages of ripening, showing an interesting technique to delay ripening in warm viticulture areas.