TAU research discovers genetic link between today’s wines and those of a millennium ago

Ancient local winegrape seeds from Shivta. Photo: Professor Guy Bar-Oz, University of Haifa.

One seed was found to belong to a variety still used to make high-quality red wine

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A new study from the Steinhardt Museum of Natural History at Tel Aviv University (TAU) and the University of Haifa found that an ancient winegrape seed discovered at an archaeological excavation in the Negev to be almost identical with the Syriki variety, which is used today to make high-quality red wine in Greece and Lebanon. Another seed is a relative of the white variety called Be’er, still growing in deserted vineyards in the dunes of Palmachim.

The genetic study was led by Dr. Pnina Cohen and Dr. Meirav Meiri of the Steinhardt Museum’s Paleogenetic Laboratory. The seeds were found at archaeological excavations led by Professor Guy Bar-Oz of the School of Archaeology and Maritime Cultures at the University of Haifa, in collaboration with researchers from the Israel Antiquities Authority. The paper was published on April 17, 2023, in PNAS.

“Archaeological excavations conducted in the Negev in recent years have revealed a flourishing wine industry from the Byzantine and early Arab periods (around the fourth to ninth centuries A.D.), especially at the sites of Shivta, Haluza, Avdat, and Nizana, which were large, thriving cities at the time,” Professor Bar-Oz says. “The findings include large winepresses, jugs in which the wine, exported to Europe, was stored, and grape seeds preserved for more than a thousand years. This industry gradually declined following the Muslim conquest in the seventh century, since Islam forbids the consumption of wine.

“The cultivation of winegrapes in the Negev was renewed only in modern times, in the state of Israel, mostly since the 1980s. This industry, however, relies mainly on winegrape varieties imported from Europe.”

One especially interesting finding was a large hoard of grape seeds, discovered on the floor of a sealed room at Avdat. The researchers say that these seeds have been relatively well preserved thanks to protection from climatic phenomena such as extreme temperatures, flooding, or dehydration. In the hope of discovering which varieties they might belong to, the researchers prepared to extract their DNA in the paleogenetic lab.

“The science of paleogenomic uses a range of advanced technologies to analyze ancient genomes, primarily from archaeological findings,” Dr. Meiri explains. “Since the DNA molecule is very sensitive and disintegrates over time, especially under high temperatures, we usually get only small pieces of DNA, often in a poor state of preservation. To protect them we work under special conditions: the paleogenetic lab is an isolated clean laboratory, with positive air pressure that keeps contaminants out, and we enter it in sterilized ‘spacesuits’ familiar to everyone from the COVID pandemic.”

The researchers first looked for any organic matter remaining in the seeds. For this purpose they used FTIR (Fourier-transform infrared spectroscopy), a chemical technique that applies infrared radiation to produce a light spectrum to identify the sample’s content. Finding remnants of organic matter in 16 seeds, the researchers went on to extract DNA from these samples.

The extracted DNA was sequenced, with an emphasis on about 10,000 genomic sites where variety-specific features are usually found, and the results were compared to databases of modern grapevines from around the world. In 11 samples, the quality of genetic material was too poor to allow any definite conclusions. Three of the remaining samples were identified as generally belonging to local varieties. Finally, the two samples of the highest quality, both dated from around 900 A.D., were identified as belonging to specific local varieties that still exist today.

The discovery was quite extraordinary. One seed was found to belong to Syriki, a known Middle Eastern variety with a long history of cultivation in the Southern Levant and Crete, still used today to make high-quality red wine in Greece and Lebanon. Since winegrapes are usually named after their place of origin, it is quite possible that the name Syriki is derived from Nahal Sorek, an important stream in the Judean Hills.

The other high-quality seed was identified as related to Be’er, a white winegrape variety still growing in the sands of Palmachim on Israel’s seashore, in remnants of vineyards probably abandoned in the mid-twentieth century. For the first time ever, the researchers were able to use the genome of a grape seed to determine the color of the fruit, discovering that it was in fact a white grape, the oldest botanical specimen of a white variety ever identified. Be’er, a unique local variety endemic to the land of Israel, is used today by the Barkan winery to make a special white wine of its own.

“The wonderful thing about paleogenetics is that sometimes tiny items can tell a big story,” Dr. Meiri concludes. “This is exactly what happened in this study. With just a bit of DNA extracted from two grape seeds we were able to trace continuity in the local wine industry from the Byzantine period, more than a thousand years ago, to the present day. We believe that our findings are also significant for Israel’s modern wine industry, which has been growing and thriving in recent decades.

“Our study opens new paths for restoring and improving ancient local varieties, to create winegrapes that are more suitable for challenging climatic conditions such as high temperatures and little rainfall.”

Other participants in the study included researchers from the University of Haifa, the Weizmann Institute, and Bar-Ilan University; and research institutions in France, Denmark, and the UK.

"Our study opens new paths for restoring and improving ancient local varieties, to create winegrapes that are more suitable for challenging climatic conditions."