Researchers Unveil Disease-Resistant Glera Clones

At Vinitaly 2026, researchers and growers presented a new set of Glera clones designed to resist the main vine diseases while keeping the grape’s original identity intact, a project that has been under way since 2015 through work by Vivai Cooperativi Rauscedo and the University of Udine. The tasting, held during the masterclass “Innovation, Sustainability, Resistance: The New Coordinates of the Glera of the Future,” brought together eight wines made from four experimental clones grown in two sites, Refrontolo in the Conegliano Valdobbiadene hills and Rauscedo in Friuli, and compared them with the standard Glera clone VCR101.

The new selections, currently identified as Glera R2, VCRR4, VCRR5 and VCR151199, were chosen from 80,000 seedlings after years of screening for resistance to downy mildew and powdery mildew. The goal was not to create a different grape, but to preserve the sensory profile associated with Glera while reducing the need for vineyard treatments and improving adaptability in the denomination’s growing areas. Diego Tomasi, director of the Conegliano Valdobbiadene Prosecco Superiore Docg consortium, and Yuri Zambon, director of Vivai Cooperativi Rauscedo, led the presentation.

Tomasi traced the effort back to earlier waves of vine disease in Europe, when growers first turned to American vines and later to hybrid breeding programs in search of resistance. He said those early solutions often came with unwanted aromas and limited wine quality. Over time, breeders in France, Germany and elsewhere produced thousands of hybrids and rootstocks, but only a small number proved useful for grapes intended for fine wine. In Italy, research accelerated again in the late 20th century as environmental concerns grew and studies showed that vineyards accounted for 80% of pesticide use on just 8% of cultivated land.

The Udine program began in 1998 and marked what researchers describe as a third generation of resistant varieties, built through controlled crosses that kept a large share of the noble parent’s genome. Later work with Vivai Cooperativi Rauscedo expanded that effort into a fourth generation focused specifically on Glera. Zambon said these are not genetically modified plants created in a laboratory. Instead, pollen from resistant donors is used to pollinate Glera in a process that mirrors natural breeding but is directed by researchers. The resulting vines are resistant rather than immune, he said, so some fungicide protection remains necessary, though at reduced levels.

The tasting showed how much site conditions still matter. The Refrontolo vines were grown on a hillside with about 20% slope and poor soil, where only three treatments were applied compared with an average of nine or 10 in conventional management. The wines were made under identical microvinification conditions at VCR to allow direct comparison.

The standard VCR101 sample showed the familiar pale color and fine mousse associated with Glera. On the nose it leaned more toward fruit than flowers, with ripe apple, pear, acacia blossom and jasmine, plus a hint of citrus peel and stone. In the mouth it was dry and firm in its bubbles, with apple skin acidity and a finish marked by bitter almond.

R2 from Refrontolo showed three genes for resistance to downy mildew and three for powdery mildew, which researchers described as the highest level currently available. It ripened slightly earlier than standard Glera and produced less fruit on average. In the glass it was similar in color but more defined aromatically, with yellow flowers such as daisy and iris, gardenia, nectarine and juicy pear. The palate was more savory than fresh, fuller and broader than the reference wine.

The same clone grown in Rauscedo felt fresher from the start, with finer but more numerous bubbles. Its aromas suggested pineapple, white melon and citron with chalky notes. The palate was fresh, savory and slender, at times citrus-driven but creamy on the finish.

VCRR4 from Refrontolo carried three genes for downy mildew resistance and one for powdery mildew resistance. Its yield matched standard Glera at about 200 quintals per hectare and its harvest timing was average for the variety. The wine was delicate in color with fine bubbles and an elegant nose of wisteria, pear skin, unripe plum, white rose and white melon. On the palate it was intense, creamy and savory, with a rocky texture and lemon peel brightness.

The same clone from Rauscedo was more open aromatically and showed larger bubbles that moved more slowly in the glass. It offered yellow flowers, orange blossom peel and pineapple on the nose. In the mouth it was broader and more textured than its Refrontolo counterpart, less refined but fuller and slightly balsamic.

VCRR5 from Refrontolo combined two genes for downy mildew resistance with four for powdery mildew resistance. It also matched standard Glera in yield while ripening slightly earlier. Its aromas overlapped with VCRR4 but seemed finer, showing apple and pear alongside cyclamen, chalk and a light mint note. The palate was creamy with a cedary grip and a slightly bitter almond finish.

The Rauscedo version of VCRR5 leaned more clearly toward citron peel, sweet acacia blossom and white melon with a faint saline edge. Its mouthfeel was earthy and stony, shorter than some of the others but savory and floral at the end.

VCR151199, grown only in Rauscedo because it is one of the latest selections from this breeding line, carried two genes for downy mildew resistance and three for powdery mildew resistance. It also yielded 20-30 quintals more per hectare than standard Glera while ripening at about the same time. It showed a finer but faster mousse and a deeper color in the glass. Aromas ranged from ripe pear and apple to white melon, white peach, carambola and light herbal notes. The palate was fuller and more vinous than sparkling in style, ending on yellow fruit and white flowers with an almond tone that made it feel closer to an older-style Prosecco.

The varieties remain under study and are not yet authorized for use in protected designation wines. Researchers said they expect commercial availability around 2029 if regulatory steps move forward. They also said they hope to introduce them gradually into vineyards through changes to production rules approved by Veneto authorities, possibly covering up to 15% of plantings in sensitive areas near roads or schools where fewer treatments would be especially useful.

Tomasi said resistant varieties are now one of the most promising areas in applied viticultural research because they can lower environmental impact without abandoning local identity. Zambon added that having several resistant options gives growers flexibility across different sites while preserving what makes Glera recognizable. He said other crosses are already being evaluated at Rauscedo as part of a process that can take nearly two decades from first idea to market release.

Researchers also pointed to gene-editing work as another path forward because it can switch specific traits on or off without changing aroma or cellar behavior as much as traditional breeding might do. For now, though, they said crossing remains valuable because it adds biodiversity to vineyards by introducing new plants alongside existing ones. At Rauscedo alone, Zambon said they are working with roughly 40 to 60 Italian native varieties as well as Spanish and French grapes, along with entirely new selections when they show promise in both vineyard performance and wine quality.