Grape DNA Profiling w/ Carole Meredith, UC Davis & Lagier Meredith

One of the world’s leading grape geneticists, Carole Meredith, Professor Emerita of UC Davis, and owner of Lagier Meredith winery, has spent decades identifying and profiling grape varieties.  It was so interesting that the interview has been split into two episodes, this one about the background of Ampelography and DNA profiling as well as the definitions of key terms such as variety, clone, and hybrid.  The second episode features how she uncovered the history of Zinfandel and how wineries use DNA profiling in wine marketing. 

Detailed Show Notes: 

• Carole’s background
  • Worked part-time at a retail nursery, got into plant genetics, and wanted to be a flower breeder
  • Changed to doing a Ph.D. on tomato genetics at UC Davis
  • Worked in biotech for a few years on cotton, corn, and soybeans
  • She went into grapes because a position opened up at UC Davis
• Ampelography - the study of grape identification before DNA testing
  • Grape varieties identified by their leaves, which vary distinctly, not by their fruit, which look similar
  • Before DNA testing, outside experts in Ampelography would often disagree with each other on grape identification
  • The upside of ampelography is that it’s very fast. Today grapes are usually first identified by ampelography and then confirmed with DNA testing
• DNA testing for grapes
  • Started ~1991
  • Looks at segments of DNA to look at specific markers
  • Need a minimum of 6 markers to identify a variety and more to establish variety parentage
  • Vitis Microsatellite Consortium - a group of academics that came together to develop DNA markers for grapes
    • In 1-2 years, developed 100s of markers
• Grape variety definition - used differently in trade or by scientists
  • Trade definition - grapes that make different wines (e.g., Pinot Noir and Pinot Gris) are different varieties
  • Scientific definition - a cultivated variety that goes back to a single seedling, scientifically, Pinot Noir and Pinot Gris are clonal variants of a single variety
• Clones - variations within a variety
  • Clones are subtypes that have developed over time
  • Usually have something to do with the fruit (e.g., color variants like Traminer vs. Gewurztraminer, Pinot Noir/Blanc/Gris)
  • Clones arise through somatic mutations of the variety
    • Older the variety (e.g., Pinot, Syrah) - more likely to have more clones
    • Young varieties (e.g., Cabernet Sauvignon) have fewer clones (<400 years old, likely a natural seedling in the early 1700s, and likely singled out to do late budding, which provided spring frost protection)
    • Some varietals (e.g., Pinot) are more likely to have mutations
  • People need to notice a difference (e.g., looser clusters which can have less bunch rot, early ripening, which avoids rainfall during harvest, or higher sugar levels for grapes like Riesling in cooler areas) and be preferentially chosen to plant new vineyards
  • ENTAV - an institution in France that systematically identifies and registers clones
  • In Chile, Jean-Michel Boursiquot, one of the world’s top ampelographers, identified that Chileans were calling Carmenere Merlot
• Grape Families
  • A term with no scientific meaning
  • E.g., Muscat - “muscat” is a type of flavor; all current varieties likely descendants of a couple of ancient varieties
  • Every variety is descended from 2 parent varieties
• Hybrids
  • Genetic/scientific definition of a hybrid is an offspring of 2 different parents of the same OR different species (e.g., Cabernet Sauvignon is technically a hybrid of Cabernet Franc and Sauvignon Blanc)
  • Interspecific hybrid or cross is an offspring of parents from different species (e.g., hybrids of American and European grape varieties used to try and combat phylloxera)

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