After decades of speculation, the origin of Zinfandel is now more history than mystery.

A UC Davis research group, working in collaboration with scientists in Croatia, has confirmed through DNA tests the Old World origin of Zinfandel -- and it's not Italy.

"Zinfandel comes from Croatia," says Carole Meredith, a UC Davis grapevine geneticist. "The grape we call Zinfandel and the grape the Italians call Primitivos are both Crljenak Kastelanski."

Meredith's research proves conclusively that Zinfandel is the same as Crljenak Kastelanski, a grape variety from the Dalmatian Coast of Croatia. Zinfandel is acclaimed as California's signature grape in the state's $17 billion wine industry. Its origins answer a question that has fascinated wine lovers and scientists for more than 100 years.

Using DNA-profiling techniques, Meredith's group and two Croatian scientists, Ivan Pejic and Edi Maletic at the University of Zagreb, discovered in December 2001 that Zinfandel and the indigenous Croatian grape called Crljenak are one and the same.

Meredith delivered a presentation June 15 on their work at the Conference on American Zinfandel in Rohnert Park, Calif. Meredith has also discovered the parents of Cabernet Sauvignon, Chardonnay and Syrah.

The modern search for Zinfandel's roots dates back to the late 1960s when a U.S. Department of Agriculture researcher based at UC Davis noticed that the Primitivo grape widely cultivated in the Puglia region bore a strong visual resemblance to Zinfandel. But no conclusive proof was possible before the age of DNA testing. Then, in May 1998, Meredith, Pejic and Maletic searched many different vineyards and some of the islands offshore Croatia's Dalmatian coast. Meredith brought back 150 samples to UC Davis for comparison with Zinfandel and Primitivo samples. But none of those was a match.

In the years that followed, Pejic and Maletic continued the search and found Crljenak in September 2000. DNA tests in Meredith's lab in December 2001 confirmed that Crljenak and Zinfandel were the same variety.

Meredith said the mystery is not quite over. She speculated that Crljenak could possibly have been brought to Croatia from Greece or Albania. However, the presence of one confirmed offspring and many other very closely related varieties in the region indicate that the variety has been in Croatia for a long time.