Showing posts from June, 2018

Evaluation of induced mutation methods in Pinotage to increase genetic variability

By Phyllis Burger Current Winetech funded project : This project aims to develop a method to increase the genetic diversity of Pinotage. Pinotage, South Africa’s locally bred cultivar, is considered the country’s flagship red cultivar, however very few clones are available to the industry. Pinotage was only bred in the twentieth century (1925) and can be regarded as a “young” cultivar. This means it has had limited time to give rise to mutations compared to other cultivars that have been around for centuries. Traditional breeding involves crossing two parent cultivars and since grapevine is a heterozygous crop, their off-spring are unique individuals with characteristics varying from both parent cultivars and from its siblings. Thus traditional cross-breeding is not suited to improve or alter single or limited characteristics of an existing cultivar. Genetic modification provides an ideal solution since specific genes can be inserted into an existing cultivar, but there is a lot

Can gene expression shed light on the “old vine” character of wines?

By Johan Burger In South Africa, as in other grape-growing areas, there is a newfound interest in old vines and vineyards, and the exceptional wines made from them. Wines produced from older vines are generally accepted as having more depth and complexity than those produced from younger vineyards, and this term is used on wine labels to indicate a wine of high quality. Nonetheless, no formal classification exists to classify a vine as an “old vine”, and it largely depends on the history of vineyards and winemaking in the area. For example, in old-world wine production areas many vineyards in excess of 100 years may exist. In contrast, in a new world growing area, a vine of 50 years might be considered old. In South Africa, the economic life of a vineyard is an average of 20 to 25 years, and vines are generally considered to be old when they reach 35 years. Describing wines made from old vines as having more depth and character is subjective, and to our knowledge no scientific re

The Pinotage genome: stress response genes are a major source of inter-cultivar genetic diversity

By Beatrix Coetzee Grapevine cultivars display a great level of intra-species diversity in viticultural and oenological traits. Understanding this genetic diversity is an important step towards developing improved grapevine cultivars, but also for the conservation of the important traditional cultivars. This study focused on the next-generation sequencing and bioinformatic analysis of the Pinotage genome and transcrip- tome. Pinotage is an artificial Pinot noir/Cinsaut cross, created with the South African climate and growing conditions in mind. Today it is  a commercial cultivar, used for  the production  of premium wines, and  deeply rooted in the South African wine culture and history. A de novo assembly strategy was followed to produce the first Pinotage draft genome sequence. Sequencing read data were also aligned to the available reference Pinot noir genome, and from this alignment the Pinotage/Pinot noir variant density, determined. Pinotage genome and transcriptome d

The impact of grape berry ripeness level on berry and wine composition & potential wine style of Pinotage

By Etienne Terblanche Current Winetech funded project: The realities of changes in consumer trends and the pressure on winemakers to create a wine that is appealing and unique, yet typical of the variety, necessitate a profound knowledge of the variety and its interaction with the biotic and abiotic environment. In comparison to many other widely cultivated “international” varieties, limited information is available to producers regarding the relationship between the berry ripening stage and wine quality of South African variety: Pinotage. Ripening stage is known to change wine phenolic content, colour, volatile composition and sensory profile. Yet the extent- and impact of these changes on wine qualitative and sensory properties specifically for Pinotage are still very broadly defined and lacks varietal specific information. The current study proposes a detailed characterisation of vineyard status in parallel to the tracking of wine composition over a range of ripening stage

Poor budburst and dying of single spurs in S. blanc and Cab. Sauvignon

By Lucinda Heyns The aim of this study was to investigate the cause of poor budburst and dying of single spurs in Sauvignon blanc (SB) and Cabernet Sauvignon (CS). Project layout: Surveys of 17 affected SB vineyards and 19 CS vineyards were conducted and the incidence and severity of spur dieback was determined Ten dying spurs were collected from each vineyard to conduct fungal isolations from 2013-2016 Field trials were conducted to determine the effect of the time of clean pruning on dieback of spurs, vine vigour and the incidence of trunk disease pathogens During the 2015 season, shoots in the three vineyards used for the clean pruning trial, were also examined for the presence of the bud mite, Colomerus vitis . Results:                                                               Isolation results show that grapevine trunk disease pathogens could be implicated in the poor budburst and dieback of spurs. Most of the dying spurs collected were obse

Brettanomyces mechanisms of survival

Winetech Final report:   The objectives of this study were to investigate the adaptation mechanisms of Brettanomyces bruxellensis to wine and to sulphur dioxide (SO 2 ). In particular, the nutritional requirements of B.  bruxellensis were investigated in the presence/absence of oxygen, together with its nitrogen uptake in the presence/absence of SO 2 . Furthermore, its broader response to SO 2 was investigated using a variety of approaches, from microscopy to transcriptomics (the expression of genes at any given time). Experimental layout: A synthetic wine medium was developed to perform the experiments of this study. Various environmental conditions were applied (e.g. presence/absence of oxygen, presence/absence of SO 2 ) and a variety of analyses were performed including microbiological analyses (population dynamics and fermentation kinetics), chemical analyses (carbon and nitrogen sources), microscopic analyses using optical and electron microscopy, as well as transcrip