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Paolo Storchi Due to climate change, experts are recommending a switch to more heat-resistant grape varieties for the entire southern Mediterranean region. But what does this mean for a growing region like Tuscany, which is characterised by traditional varieties? Markus Blaser talked about this with the agronomist Paolo Storchi. He does research at the CREA Institute for Viticulture and Enology in Arezzo and is a member of Florence's GeorgofiliAgricultural Academy.

Will winegrowers in the southern Mediterranean soon have to plant heat-resistant grape varieties because of climate change?

Storchi: The grape varieties of the southern Mediterranean are quite heat-tolerant, and a little further north, viticulture is suffering more from climate change. But in addition to the rise in temperature, we are registering a different distribution of precipitation compared to the past. Therefore, agriculture is shifting to higher or more northerly areas where temperatures are somewhat cooler. The grape varieties of the south will migrate to the north.

What does that mean for viticulture in Italy?

Storchi: The trend could be to plant grape varieties that are better adapted to hot environments. The Montepulciano variety, for example, thrives magnificently in the south, but could also spread northwards. However, it becomes problematic above all for cultivation areas with controlled designation of origin and defined wine typologies. The production rules that apply there have so far prohibited the use of other grape varieties. We experimented with Nero d'Avola from Sicily a few years ago: Indeed, this variety produces good results in Tuscany. But because it is not a traditional variety of the region, it is hardly grown by the wineries. Changing grape varieties is more difficult in European viticulture than in Australia or California, for example, where the regulations are less strict.

Nevertheless, in Bolgheri they are already talking about replacing Cabernet Sauvignon and Merlot with Cabernet Franc.

Storchi: Cabernet Franc is already grown there. In fact, Merlot is currently having problems on the Tuscan coast because it ripens early and reacts very sensitively to heat. Cabernet Sauvignon, however, proves to be extremely stable and adaptable to environmental influences. That is why it is a very common international grape variety: it produces fairly similar results wherever it is grown. The differences to Cabernet Franc are rather small - but all the greater to Sangiovese, which reacts extremely strongly to environmental conditions. That is why its cultivation is only promising in a few areas. This also applies to Nebbiolo in Piedmont: outside its region of origin, it adapts poorly.

Like Sangiovese, Nebbiolo adapts poorly outside its area of origin.

Sangiovese shapes the character of Tuscan viticulture.

Storchi: Replacing it there would be very difficult, also from a research point of view. That's why we are thinking less about changing varieties and instead experimenting with rootstocks that can cope better with drought stress. If the roots can absorb more water, the heat is better tolerated. The rootstocks used today were selected 100 years ago and are no longer suitable for the current situation. The University of Milan has recently provided four new rootstocks, but we are still at the very beginning and should definitely increase research in this field. Because rootstocks are not affected by the restrictions of the growing regions - they can be exchanged without having to throw the variety list overboard. However, today we are mainly researching disease-resistant grape varieties. But these tend to ripen early, which is why we run the risk of having to harvest the grapes as early as the beginning of August. Therefore, our aim in genetically modifying the grape varieties is to delay their growth so that the grapes do not ripen in the hottest period.

Are there already first results for Sangiovese or other varieties?

Storchi: The difference between early and late ripening Sangiovese clones is at most one week. So we can't expect much from clone selection for Sangiovese, but Colorino could be a possibility. In addition, we can recover and enhance the germplasm of old, less appreciated but particularly late-ripening varieties. Gralima, for example, has only recently been registered in the national grape variety register. It was formerly known as "Lacrima di Val d'Arno" (Tear of the Arno Valley) and ripens towards the end of October, very late. It could therefore be quite interesting for a more balanced ripening process. However, like clone selection, the detection of such varieties is long-term research.

How can winegrowers better adapt to climate change in the short term?

Storchi: They can change their cultivation methods and, for example, expose the grapes less to direct sunlight. They can also protect the leaves from excessive evaporation by treating them with natural kaolin, for example. Late pruning in winter can also postpone the entire vegetation cycle by a few days and thus delay ripening. In the medium term, we should plant vineyards at a slightly lower density than before: If we give the vines more space, we make it easier for them to absorb water through the roots. The biggest problems facing viticulture are climate change and sustainability. These two topics will keep us busy in research for the next ten, twenty years.

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Markus Blaser works as a freelance journalist and historian in Florence. The Swiss wrote for "Merum" until 2016 and publishes on the economic, political, cultural and historical background of wine and olive oil in Italy.

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