Solved: The Great Zinfandel Mystery


One of the biggest mysteries in the wine world appears to be solved. A UC Davis plant geneticist has confirmed the Old World origin of Zinfandel--and it’s not Italy.

“Zinfandel comes from Croatia,” says Carole Meredith. “The grape we call Zinfandel, and the grape the Italians call Primitivo, are both Crljenak Kastelanski.”

That’s Crljenak Kastelanski: pronounced tsurl-YEN-ahk kahstel-AHN-ski. Its discovery answers a question that has fascinated wine lovers and scientists for more than 100 years: Where did California’s signature wine grape come from?


Meredith’s research culminates a 35-year search by two generations of scientists facing nearly impossible odds. With more than 10,000 grape varieties in the world, locating Zinfandel’s Old World source was like finding the proverbial needle in the haystack. In fact, Crljenak is a forgotten variety in its homeland, Dalmatia, and the more than 1,000 islands off its coast in the Adriatic Sea. So far, Meredith and her team have found only 20 Crljenak vines, planted among other grapes in three locations.

But 20 vines is enough to rescue the original Zin from oblivion--and that’s important well beyond the satisfaction of establishing Zinfandel’s pedigree. Aside from giving Zin new legitimacy among the wine world’s leafy aristocrats, the discovery closes the genetic gap between modern California Zinfandel vines and their ancient forerunners. Who knows what sensory delights await Zin lovers once the old Croatian clones become part of the California vineyard mix?

When Meredith revealed her finding casually to friends and colleagues this spring, the news electrified the wine world. She will formally present her discovery in August at a grape genetics conference in Hungary. She is also working on a paper to be published early next year in the Journal of Enology and Viticulture.

The quest to solve the mystery of the Mystery Grape is a scientific whodunit with a diverse cast of characters. When Meredith became the chief detective on the case in 1991, it had already been in progress for decades. UC Davis professor Austin Goheen and graduate student Wade Wolfe laid the groundwork in the 1960s and ‘70s. The legendary Napa Valley vintner Miljenko “Mike” Grgich, a native Croatian, was a key informant. The investigative team included scientists, historians, grape growers and students in California, Italy and Croatia.

Serendipity played a part, too. One of the most important contributions was made by a Croatian student at UC Davis. Jasenka Piljac was a dishwasher in Meredith’s laboratory in the early ‘90s. After graduating from Davis and returning to Zagreb, Piljac served as translator and research assistant during Meredith’s 1998 sleuthing mission. “The timing worked out very well,” says Meredith. “I would not have been able to do it without her. And that’s an example of the almost eerie way things have fallen into place on this quest.”

The mystery of Zinfandel has haunted wine lovers and viticulturists for more than a century. Unlike every other fine wine grape in the state, Zin apparently had no European homeland. Cabernet came from Bordeaux, Chardonnay and Pinot Noir from Burgundy. But for all anyone knew, Zinfandel came from outer space.


Recent historical research, largely by wine historian Charles Sullivan, has revealed that the first “Zinfendal” vine appeared in a Long Island, N.Y., nursery in the 1820s. It may have come from the gardens of the Austrian imperial palace in Vienna, which in the 18th century included vines from every part of the empire, then including Croatia. Once in the United States, the vine went out West just after California’s statehood in 1850, and it is thought to have shown up in the Sonoma Valley in 1859.

It arrived in the midst of viticultural mayhem. Because California has no native wine grapes, hundreds of grape varieties were being imported and planted during that period of explosive development. Some were misnamed, others were known by multiple names. Zinfandel was just a face in the crowd.

Yet within a few decades it was the most planted red grape in the state; only in 2000 was it finally overtaken by Cabernet Sauvignon. Ultimately, Zinfandel became the symbol of California wine.

Fast-forward to the late 1960s. Goheen, the legendary UC Davis viticulturist, is traveling in Southern Italy in Puglia, near Bari. He tastes a spicy, berryish wine that strongly reminds him of Zinfandel. He asks to be taken to the vineyard--and finds himself looking at vines that appear to be Zinfandel. His hosts call the vines Primitivo.

That got the wheels turning. Goheen brought Primitivo cuttings back to California and confirmed that--visually, at least, since DNA testing wasn’t yet available--they seemed indistinguishable from Zin. Shortly thereafter, Wolfe, a doctoral candidate in plant genetics, announced to the American Society of Enology & Viticulture that isozyme analysis (a precursor of DNA testing) showed that Zinfandel and Primitivo were probably the same.

The Cutting Edge

By the late 1980s, DNA profiling was developed to a high degree of accuracy, and Meredith was on its cutting edge. She used it to demonstrate that the grape known as Pinot Blanc in California was different from the French Pinot Blanc and was, in fact, the obscure variety called Melon. Meredith’s assistant, graduate student John Bowers, would later use the same techniques to show that Cabernet Sauvignon was an offspring of Sauvignon Blanc and Cabernet Franc.


Now, Meredith turned her attention to Zinfandel and Primitivo. “Here was a mystery, and I thought I could find the answer,” she recalls. “That was the scientific driver.” But there was more to it than just the challenge. “Since we know what part of Europe all our other varieties came from, we know where to look for new clones that will give us diversity in California vineyards,” says Meredith. “With Zin, all we could do was look in old California vineyards. But if we knew where it came from, we could look there and find more diversity to greatly improve the range of clones.”

The DNA tests used on plants are the same as those used on humans. Tissues (whether blood, muscle or leaf) are subjected to chemicals that dissolve components progressively until all that’s left is a clear substance containing DNA molecules, each composed of sequences of nucleotides repeated over and over. A machine scans the isolated DNA for specific sequences, marks them and makes millions of copies that are finally visible as bands on gel. Then they can be compared with DNA from other plants.

In 1992, 25 years after Goheen’s suspicions were aroused, Meredith ran a DNA test on tissue samples from Primitivo and Zinfandel vines. They appeared to be indistinguishable. But the tests were still rudimentary, so it wasn’t until 1995 that a more advanced DNA analysis convinced Meredith that the two vines were, in fact, the same variety.

But what did that mean? Primitivo was not a native Italian grape. Sullivan and other historians believe it may have been introduced during the 18th century, possibly by Catholic monks. However, no wines were labeled Primitivo before the 1890s, long after Zin was established in California. In any case, the true homeland of Primitivo-Zinfandel was unknown.

Is it the Same?

In the early 1980s, the writer Leon Adams suggested that Zinfandel might be the same as Plavac Mali, a widely planted Croatian red grape that yields a berryish, tannic wine similar to Zin. That idea was pressed in the ‘90s by Mike Grgich, who had immigrated from Croatia as a young winemaker in the 1950s and gone on to become a pillar of the Napa Valley wine community. Grgich (who produces a Plavac Mali wine in Croatia under the Grgic label) became a prime motivator in the Zin quest, directing the detectives to promising sites in his native country.

There were Plavac Mali vines in the UC Davis collection, and some appeared to be indistinguishable from Zinfandel. However, Meredith’s tests during the late ‘90s gave mixed results. Knowing that mislabeling of vines in institutional collections is common, she decided to go to Croatia and collect samples herself.


No sooner had she started planning a trip than she got an e-mail from University of Zagreb genetics professor Ivan Pejic asking for advice on a new project to study the indigenous grapes of Croatia. “That’s when I said, ‘I’m coming over there, so why don’t we work together?’ ” recalls Meredith.

In spring of 1998 she traveled to Croatia and met Pejic and his colleague, viticulturist Edi Maletic. With Piljac, Meredith’s former lab student, they traveled through the Dalmatian Coast and islands, taking tissue samples from about 150 Plavac Mali vines in 40 vineyards. Back in her lab at UC Davis, Meredith ran the DNA tests.

The results were disconcerting. Plavac Mali was not Zinfandel. However, it appeared that one was a parent of the other, although it wasn’t clear which way the genes went. The game was still afoot.

Meanwhile, Pejic and Maletic devoted themselves to walking vine rows in Dalmatia, looking for Zin-like leaf shapes in the spring and Zin-like fruit in the fall. Finally, in September 2000, they found another likely suspect in a mixed planting of old varieties. It was a single specimen of an obscure old variety called Crljenak Kastelanski (meaning red grape from Kastel, a town near Split). Still lacking the funds for expensive DNA analysis, they sent tissues from the vine to Meredith for testing in her UC Davis lab.

No dice. The vines didn’t match, and at that point it looked as though the search had hit a dead-end.

Yet everyone agreed Crljenak really, really looked like Zin. So Pejic and Maletic went back to the vineyard--a six-hour trek by car from Zagreb to the coast--where they realized that in the thick tangle of canes they had mistakenly taken tissue from the shoot tips of a neighboring vine. This time they made sure their sample was from the Crljenak vine before they sent it to California.


Bingo. A perfect DNA match linked Crljenak, Zinfandel and Primitivo. On Dec. 18, 2001, she recalls, Meredith e-mailed Pejic, saying, “I’m convinced.” Subsequent testing of samples from other vines provided a bonus revelation: Plavac Mali is an offspring of Crljenak and another Croatian grape, Dobricic.

Now that Crljenak has been rescued from its precarious position--literally on the brink of extinction--the next step is to look for more Crljenak vines.

The variety was virtually wiped out by vine diseases in the 19th century, then further reduced during the Communist era when the native grapes were systematically replaced by high-yielding varieties suitable for mass production.

Widening the Pool

The goal is to widen the pool of possible clonal material that can enrich the grape’s diversity. Selections from Croatia will complement the Zinfandel Heritage Vineyard, a one-acre Napa Valley planting of Zinfandel selections taken from old vineyards throughout California by UC Davis clone specialist James Wolpert and his team.

The ongoing search for Crljenak in Croatia, led by Pejic and Maletic, is being substantially funded by several California wine producers, led by Ridge Vineyards. The Croatians are focusing on the large island of Solta, just off the Dalmatian Coast from Split. The vineyards on Solta include quite a bit of Dobricic, which makes it likely that Plavac Mali’s other parent, Crljenak, may be found there, too. “It makes sense that if they got together, they must have been growing fairly close together,” notes Meredith. “So Solta is a strong possibility.”

Meanwhile, California producers have begun to propagate both Primitivo and Plavac Mali and make wine from the grapes (try Tobin James Cellars Primitivo ‘99, “James Gang Reserve”). And Crljenak has been propagated at UC Davis. Cuttings will be available to growers within a year or so, which means we could begin to see California Crljenak wines as early as 2006.


And then we’ll find out from a sensory standpoint if it’s all just a matter of names. Will, in fact, a Zin by any other name smell as sweet?