Cracking the code to genetic diversity in wine

Darren Smith

Darren Smith

17 May 2018

Broadening the gene pool is the best way of ensuring healthy vines, and with pressure on to reduce the use of pesticides, it’s something that’s of growing interest to vine scientists. Darren Smith investigates a world of  cross-breeds, hybrids and genetic markers

Genetic diversity is desirable in any context. It serves as a way for populations – humans, vines or any other biological entity – to adapt to changing environments and survive. In the wine world, prompted by the pressures of climate change, environmental sustainability and disease, growers are coming to realise that they ignore this fact at their peril.

The nub of the problem is that the modern vineyard practice of clonal selection of Vitis vinifera, which replicates the best vine material, has artificially narrowed the genetic diversity of vines.

Healthy hybrids

What’s needed, some producers now realise, is a shift in mindset away from ‘elite’ cultivars and towards rediversification, favouring more obscure varieties and breeding new disease-resistant hybrids to ensure long-term sustainability.

‘We are more and more pushed by public powers, and also by the wine industry, to provide tools to reduce the use of pesticides,’ says Laurent Audeguin, lead agronomist at the department of plant material at the Institut Français de la Vigne et du Vin. ‘One good answer could come from doing breedings between siblings coming from the [vine] species of North America and our historical cultivars.’

In France there are high hopes for four new hybrid varieties – Vidoc, Artaban (red), Floreal and Voltis (white). The fruit of a decade’s work, these are cross-breedings of vinifera with US species Vitis rotundifolia and Asian species Vitis amurensis. They offer strong resistance to downy and powdery mildew, and should be authorised for commercial use this year. Audeguin expects a further 20 to 25 new French varieties to emerge in the medium term.

This is a significant step forward, but there are other viral diseases (leaf roll and Pierce’s disease) and wood-decaying fungal diseases (Esca, Eutypa) to consider, which are genetically more complex and will take considerably longer to tackle.

‘Wood decay is more complex than for mildews,’ Audeguin explains. ‘In the case of downy and powdery mildew, only a small number of genes have been identified; for wood decay, it is far more complex.

‘We know for a fact that Savagnin and its progeny, like Sauvignon and Chenin, are very susceptible to wood decline. At the opposite end, Merlot or Cabernet Franc are less susceptible and that needs to be investigated. But that will take a long time.’

Dr Greg Dunn, Australian viticulture specialist and MSc Viticulture and Oenology programme manager at East Sussex’s Plumpton College, recognises the urgent need to tackle disease and reduce the need for pesticide sprays, but says fruit quality has to be there too.

There is no point introducing these vines unless the wine quality is there

Dr Gregg Dunn

‘If we can substantially reduce, or even eradicate, sprays, it’d be fantastic, but it takes time to assess fruit quality, and there is no point introducing these vines unless the wine quality is there,’ he says.

There is a set of new disease-resistant red and white hybrids planted by Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) in the Barossa Valley and New South Wales that are better suited to local growing conditions. These are based on a molecular technique known as marker-assisted selection, which dramatically advances traditional breeding. It will, however, take time for them to produce fruit, and for the wines to be evaluated.

Australian wine producer Brown Brothers is growing other CSIRO-produced hybrids with a range of yield and winemaking attributes. But again, Dunn notes, it is early days.

‘They may perform remarkably well in terms of disease,’ he says, ‘but it’s a case of starting to make wine from them before you work out where they’re going to fit.’

Hotter climates

Disease pressure is one thing, but arguably the biggest determining factor in changing the way the wine industry works will be climate change.

‘Climate change is fascinating,’ says Dunn. ‘Arguably, the most important determinant of fruit composition and wine sensory quality is temperature. So as temperature continues to rise, the sort of wine styles that regions are known for are inevitably going to have to change.’

We may see, for example, more Aussie Assyrtiko, as pioneered by Clare Valley producer Jim Barry. Similarly, in Bordeaux, Audeguin highlights longer-term potential for phasing out early-ripening Merlot – currently 60% of the region’s vineyards – in favour of later-ripening varieties like Petit Verdot and Cabernet Franc.

‘If a region in Australia is used to growing a particular white variety, for instance, and the weather is getting hotter, it would be fantastic for them to change to one of the exciting ‘alternative’ varieties from hotter Mediterranean regions – but markets need to support such changes,’ says Dunn.

Has the wine industry been slow to react to this need to broaden the gene pool? Undoubtedly. It’s up against a long tradition that is resistant to change, but it is happening. In Burgundy, for instance, The Bourgogne Wine Board is now supporting a regional conservatory for Pinot Noir and Chardonnay that will make its first plantation of genetically diverse plant material this year.

Such initiatives are starting to emerge all over the Old and New World. As is typical in the wine industry, it will just take time for them to bear fruit.

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