Wine’s genetic diversity: Thank goodness we’re not coffee

Wine has a diversity issue. Wine actually has several diversity issues, but I’m not prepared to deal with the massive and significant question of non-white non-male winemakers (today). The much easier diversity question is about the wine grapes themselves. And even though it’s an issue, and one that’s been rightfully earning more press of late, wine grapes have the potential to be a good deal better off than most crops. The problem is of our own making, and we should be able to unmake it.

Arabica coffee varieties, according to a recent genetic survey, share 98.8% of their genes in common. That’s an estimate made by sampling both wild and cultivated plants (781 sequences in total) from around the world. So, even if coffee breeders try their darndest to increase the diversity of cultivated coffee plants – which they are, because genetic diversity means better resilience against threats like infectious diseases and climate change – they only have so much room to work. The survey found that wild plants were more genetically diverse than cultivated ones. The breeding stock can be improved. But compare coffee to maize, for which something like 30% of the genome varies across all of the plants on the planet, and there’s not that much room.

Wine grapes are like maize, not like coffee. Both maize and Vitis are, in fact, extraordinarily diverse. No shortage of room here. What’s most curious for wine grapes, though, is that the difference between the genetic diversity of wild and cultivated vines isn’t that great. When humans domesticate a species, we create a genetic “bottleneck” (Nature has a nice image here), reducing genetic variability in the new crop. For wine grapes, the bottleneck was “weak;” the reduction wasn’t that dramatic. (Coffee, by the way, suffered a very severe bottleneck.) And earlier this year, a genetic survey of wild and cultivated grapevines in the Republic of Georgia, where grapes were first domesticated to the best of our knowledge, still found plenty of diversity in wild grapevines that doesn’t overlap with cultivated varieties and which have yet to be explored.

Unlike coffee, the real problem with wine grapes isn’t that the genetic diversity isn’t available, in wild or even in cultivated plants. The problem is that we’ve artificially selected for an incredibly narrow set of vines, over and over again, through clonal selection to replicate what we think is the best of the best. To recapture the genetic diversity that might help wine combat disease and changing climates and whatever else the next century or three throws our way, we need to undo the relatively recent work of the modern wine world.

The numerous research teams working around the world on the grape diversity issue have a great big spectrum of possibility out in front of them. That’s a good reason to be hopeful. And to be sorry for the coffee guys.