Upending the story of ancient grapes: Genesis of the effort

A recently published grapevine genetic study (Y. Dong, et al., Dual domestications and origin of traits in grapevine evolution, Science 379 (6635), pp. 892 - 900, 3/3/23) "has upended the history of how humans first domesticated grapes for winemaking ..." (Melanie Lidman, It's in the DNA, Times of Israel, 3/25/23). That history had been widely accepted among wine- and grape-history researchers and had served as the jumping-off point for all of the ancient wine reporting of this blog (I have, to date, covered Armenia (wine history and winemaking), Iran, and Lebanon (the Phoenicians and Renaissance interruptus).).

The core elements of this now-discounted history was that the wine grape Vitis vinifera split from its wild progenitor Vitis sylvestris as a result of a single-point domestication event which occurred 8000 years ago somewhere in the Caucasus. From that point the domesticated cultivar spread through ancient Middle Eastern kingdoms and eventually into Europe.

According to Dong, et al., there had been previous genetic grapevine studies but "critical details of grapevine domestication were inconsistent":

• Multiple centers (Western Mediterranean, Caucasus, Central Asia) had been identified as the initial domestication site
• Three demographic inferences yielded population split times to dates between 15,000 and 400,000 years ago
• The single-origin theory did not bring clarity to the origin order as regards table and wine grapes
• One school held that wine grapes came first, with table grapes splitting off ~2500 years ago
• Several studies suggest that the earliest cultivation of European wine grapes in France and Iberia can be traced back earlier than 3000 years ago.

Those discrepancies, according to Dong, et al., arise from "inadequate sampling of grapevine accessions" (genetic material) and "limited resolution of genetic data" in prior studies.

The objectives of the Dong, et al., study were to:

1. Build a grapevine genomic dataset from a global cohort
2. Analyze the contents to: 
1. systematically delineate the structure of grapevine genetic diversity
2. explore the origin of V. vinifera
3. deduce a putative dispersal history
4. investigate key domestication traits and diversification signatures.

Before I get into the study design, implementation, and results, let me take you back to its origin story.

Origin of the Study Effort

According to Lidman, Dr. Wei Chen (Yunnan Agricultural Institution, Southwest China) began sequencing grape DNA in 2017 as part of a study on Chinese grape cultivars. The lab sequenced almost 500 grapevines and found that the DNA allowed them to track:

• the way different varieties migrated across the country
• how cultivars split off from one another to form distinct varieties.

This brought him to the realization that, with enough DNA, he could map the migration of different grape varieties through space and time.

In 2019 Dr Chen and his lab launched an international research project focusing on grape cultivars and reached out to colleagues around the world asking them to contribute material towards the study. Colleagues in Germany, France, and Spain sent either dried young leaves -- which the lab could use to extract and sequence DNA -- or sequenced DNA of local varieties. These friends and colleagues also contributed by recruiting other participants into the program.

The lab began looking for patterns in the DNA after they had received samples from 90 scientists in 70 countries.

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I will report on the study execution and findings in a subsequent post.

©Wine -- Mise en abyme