Grape Breeding

A century ago, Swiss and German viticulturists cross-bred grapes to create white wines that could thrive in their colder, northern European climates. The resulting varieties, Kerner, Müller-Thurgau and Scheurebe, are still bottled in Europe. Local production declined significantly, however, due in part to the uneven reputations of their wines. But fortunately, Kerner, Müller-Thurgau and Scheurebe also left home and thrived elsewhere. Here’s a look into these three cross-bred grapes that have found both success and struggle for a better part of a century. Kerner In 1929, German grape breeder August Herold crossed Riesling with the red grape Trollinger (also called Schiava or Vernatsch) to create Kerner, a high- yielding, aromatic and frost-resistant grape. Kerner, whose name was inspired by the German physician and poet Justinus Kerner, languished in a Württemberg greenhouse at a breeding station for decades. It wasn’t released for widespread cultivation until 1969. But the grape finally reached its peak in 1990, when it made up 7.5% of Germany’s vineyard acreage. “If you plant this grape in fertile, deep soil, you get a neutral, easy wine,” says Armin Gratl, managing director of Eisacktaler Kellerei–Cantina Valle Isarco in Alto Adige, Italy. “This was exactly what the founder wanted to create…Germany already had Riesling as a premium grape variety.” When Kerner arrived in Italy, this white grape truly thrived. Located in the northeast portion of the country, Alto Adige’s cool climate makes it a hotbed of quality Kerner production. Vineyard sites in Val Venosta and Isarco Valley, the latter where Gratl’s winemaking cooperative operates, showcase Kerner’s potential. Planted in stony soil up to 3,300 feet above sea level on mountainside slopes, Kerner vines yield less fruit and produce smaller berries, which concentrates its flavors. “You get intense, clear aromatics,” says Gratl, like ripe peaches, dried apricots, orange peel and ginger just to name a few. “The wines are juicy and powerful, with soft fruit sweetness on the finish.” But Italy isn’t the only place where Kerner found success. While it might sound like a stretch to mention Lodi, California, in the same breath as Alto Adige, Kerner has found a home in both destinations. Sonoma-based winemaker David Ramey was introduced to the grape by Paul Grieco, who poured it for him at his then-New York City restaurant, Hearth. Ramey’s heart leapt. “I loved it and had never heard of it,” says Ramey. “Kerner fills the gap in the middle, Riesling aromatics with some of Gewürztraminer’s body and midpalate.” Ramey had made long-lived Syrah, Chardonnay and Pinot Noir in California since 1996. He tracked down the only Kerner planting west of the Mississippi in Lodi for his first Kerner vintage in 2014. Now, he produces an unfiltered, bone-dry expression for his Sidebar line. Markus Niggli of Markus Wine Co., a Swiss winemaker who lives in California, also uncovered some Lodi Kerner. His version is fresh and lively. “Kerner is a fun wine,” he says. “Younger people want to try out new things. This wine is also used in white flights in wine bars. It is something different than the standard whites you find these days.” Müller-Thurgau Some wine drinkers groan at the notion of Müller-Thurgau. It has a reputation for being simple and modest, but this grape can make a big impression if handled with care. A cross between Riesling and Madeleine Royale, Müller-Thurgau was created in Germany by Hermann Müller, a professor from Thurgau, Switzerland, in 1882. When grown for high yields at low elevation, often seen at German wineries, the resulting Müller-Thurgau is as flat as its vineyards. Like Kerner, Müller-Thurgau develops character as it moves skyward. In Alto Adige, Sabine & Christof Tiefenbrunner’s namesake winery is known for its Müller-Thurgau, which they plant as high as 3,300 feet above sea level. Anything below 2,000 feet, Müller-Thurgau becomes “bland and flat,” says Christof. They like working with this cross-bred grape because it ripens in cold sites where other varieties can’t. They just make sure to regulate yields for good concentration. The Tiefenbrunners coax zesty minerality from their Müller-Thurgau, which is accompanied by notes of apples, white flowers, peach and apricot. The Müller-Thurgau from their most elevated vineyard, Feldmarschall Von Fenner, can age 20 years. Scheurebe In 1916, Georg Scheu wanted to combine the best traits of Bukettrebe and Riesling to make a grape that smells, tastes, ripens and resists frost better. A Riesling 2.0. Initially, the grape only made up 4.4% of Germany’s vineyard acreage at its peak. Today, it makes up just 1.4% of the country’s vineyard acreage. So, what happened? Highly aromatic with bracing acidity, Scheurebe was employed in cheap, sweet wines that diminished its reputation. But as a younger generation of winemakers discovered it, Scheurebe’s fortunes changed. Capable of bold orchard fruit, herbal and black currant aromatics, Scheurebe can yield exciting wines comparable to Sauvignon Blanc. Jan Eymael of Weingut Pfeffingen in Germany’s Pfalz calls Scheurebe his favorite grape. “I love the variation you can get,” he says. Pfeffingen produces dry, off-dry and sweet styles of Scheurebe, but he believes drier wines show off the grape’s finesse. “Scheurebe is sensitive,” says Eymael. “It needs a warm site with a good water supply to develop the ripeness and aroma you need for great Scheurebe.” Though most Scheurebe remains in Germany, a few vines ended up in California when Joseph Phelps brought cuttings back from the Roter Hang in Rheinhessen. Brook Bannister, of Bannister Wines in Sonoma, found them a few years ago. “There’s a lot of good Riesling made in California, so it seemed like Scheurebe, being a Riesling cross, had a good chance at working,” says Bannister. With the vineyard, owned by grape grower and winemaker Justin Miller, down the road from his house in Alexander Valley, Bannister bought up the tiny quantities of fruit available. His 2019 is a juicy, floral and lightly phenolic white wine that’s delicious and rare. “Making oddball varietals is exactly what we should be doing here because it’s anecdotal to our culture and the whole idea of California,” says Bannister. “I’m always ready for a project that will remain in obscurity and make very little money.”