Wine is one of the great joys of life and it is important to our economy. In our book Grape: Stories of the Vineyards in South Africa, Jeanne Viall, Jakes Gerwel and I used the grape to tell stories about the people who work with it as workers, winemakers, scientists, farmers and exporters. And we tell the story of Pinotage, South Africa’s only wine cultivar. 

Pinotage was developed by Abraham Perold by pollinating Hermitage (Cinsaut) with Pinot Noir to create a cross that had the best characteristics of the parents: the classic Burgundy taste with the easy-to-grow, disease-resistance of Cinsaut. His experiment yielded four seeds which were planted in his garden and later moved to Elsenburg Agricultural College.

The first commercial planting of Pinotage was on the farm Myrtle Grove near Sir Lowry’s Pass in 1943. In 1959 and 1961 Pinotages from Bellevue and Kanonkop caused a sensation at the Cape Wine Show when they emerged as champion wines ahead of classic red cultivars.

The native territory for the forebears of what became today’s domesticated grapes (Vitis vinifera) is the region that today makes up Iran, western Turkey, Armenia, Azerbaijan and Georgia,  where the ancestor to Vitis vinifera still grows wild.

A recent study of grape genes suggests that the grape was domesticated about 8 000 years ago and migrated from its Near East origins first to Western Europe and then in waves to the rest of the world, following human migration patterns. The earliest acts of cultivation favoured the self-fertilising members of the species. Over time, grape selection went through weak so-called genetic bottlenecks, meaning they retain considerable genetic diversity, offering potential to harvest desirable traits in taste and texture.

After the sequencing of the Pinot Noir gene, the Economist noted in December 2009 that the ‘battle between those who think character comes from nature and those who think nurture is the key is not confined to students of humanity’.

‘It lies at the wine-making too. For European growers, the variety of grapes is important, of course. No one would mistake cabernet sauvignon for sangiovese or riesling or chardonnay. But grape varieties are normally propagated as cuttings... clones. What creates a wine’s character, they argue, is the terroir – that mysterious combination of soil and microclimate that gives the appellations controlees their cachet... the essence of wine lies in its nurture.’

Not quite, said the plant geneticists. In genetics it is never only nature or nurture at work, but always both. Geneticists have found hundreds of genes that produce flavours and aromas in wine grapes.

Work on the grape genome shows that the parent grapes for Pinor Noir were very different, genetically. The implications are twofold: firstly, there is the opportunity to explore genetic diversity for novel flavours and aromas, and more consistently good flavours can be engineered.

Secondly, knowing these genes creates the potential to build greater immunity against plant pathogens so wine grapes can be grown in areas that might otherwise be inhospitable to the vine. Sequencing the Pinor Noir genome turned up 289 genes which relate to disease resistance. Yet in spite of this, ‘Pinot Noir remains susceptible to several fungi, bacteria and viruses possibly due to a defective system for recognizing pathogens,’ according to Science Daily. ‘Pinot Noir can be crossed with many wild grape species providing a large reservoir of disease resistance genes, which can be exploited with the aid of this genome road map.’

COP17 – the United Nations gathering to tackle climate change – is meeting soon in Durban. It’s a good time to talk about how nature, and what we have done to it, impacts on the ‘terroir’ of grapes. What are the effects of climate change on the traditional grape-growing areas of the country and which adaption strategies are best? Research shows significant trends will occur in rainfall and air temperature, and climate change is projected to lead to warmer and mostly drier conditions in the wine growing parts of South Africa. Also predicted is a higher incidence of extreme events, such as severe storms.

Records from 12 weather stations in the Cape, between 1967 and 2000, show that very warm days have become warmer, particularly during the past decade.

In the future, temperatures are expected to rise in the south western Cape by about 1.5˚C along the coast and by about 2˚C to 3˚C inland of the mountains by 2050. How will this affect viticulture? Vines are hardy and produce better fruit when made to struggle. But how much struggle can it take? 

A change in climatic patterns will affect wine production and such impacts are already being felt within the South African wine industry both directly, in terms of physical changes in climate, and indirectly, as growing environmental awareness amongst consumers drives demand for carbon-efficient produce.

The wine industry here has been characterised by its geographical diversity, but this is threatened by climate change. When a warm region becomes hotter, diversity in the type and style of wine is more limited. On the other hand, the industry is situated in an area where there is still potential for further expansion into temperate and cool areas, for changes in viticultural and oenological practices, and for changes in wine styles.

Suzanne Carter, an environmental and geographical scientist at the University of Cape Town, says climate change will impact on the SA wine industry in four main areas: changes in rainfall; extreme events; temperature; and carbon dioxide levels in the atmosphere.

Rainfall will decrease in the Western Cape, but by how much isn’t known. Most vineyards use irrigation. Currently most farmers don’t use their full quota of irrigation water and therefore could possibly draw more water as temperatures rise. As demand for water increases, wine producers will pay more per unit of water, impacting on costs.

The distribution of rainfall events is also a concern. In the past 50 years there has been an increase in the number of dry days between rainfall events. If dry-spell duration increases, the period of increased evaporation also increases. 

Peter Johnson with the UCT Climate Systems Analysis Group say: ‘Grape people don’t want rain, especially summer rain. They want dams and rivers full, but not rain.’

Extreme events are also expected to happen more often with climate change. Heavier rains, happening less frequently, are not always desirable, as a lot of water is lost to runoff. Floods may also ruin agricultural crops. Increased drought is of great concern. Irrigation can be used to offset any deficit; however, if there are water restrictions or an increased demand for water, it will become increasingly difficult to provide supplemental irrigation, writes Carter.

Temperature increases, so far, have improved the quality of wines. But  in some areas, where the warming has been more pronounced, there seems to be a threshold over which quality is sacrificed if ripening occurs too early. Each cultivar and style of wine grape will have different susceptibilities and coping ranges.

There is some speculation as to the resilience of vines to adapt to climatic stress, says Carter. Greater resilience may make the vine more water efficient; however, it’s unclear whether this may affect wine quality. Vines produce better quality fruit when they have struggled, producing smaller, better quality yield. But if yields become too small, the capital invested in the vines is not recouped in sales.

Carbon dioxide increasing in the atmosphere encourages growth of larger fruit and yields, and it increases water efficiency in the vine. But this may produce higher sugars that would change the flavours and, potentially, the quality of the grapes. 

Dr Wilmot James MP is the Chairperson of the African Genome Education Institute (AGEI) and Honorary Professor in UCT’s Division of Human Genetics. This is an excerpt of his lecture, delivered on 10 November 2011, as part of the 2011 Darwin Seminars hosted by the AGEI & UCT’s Division of Human Genetics.

The lecture was dedicated to science journalist Christina Scott who passed away on 31 October.