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California produces more than 80 percent of U.S. wine and comes in fourth in world wine production, generating more than $57 billion in state economic impact. With those numbers, it’s easy to see why it’s important for California’s vineyards to stay healthy. This Bonus Bite episode explores the future of California wine under a changing climate. Grape geneticist Andy Walker chats with Unfold about the role Texas could play in helping California vineyards adapt to warmer temperatures.

In this episode:

Andy Walker, grape breeder, geneticist and professor of viticulture and enology. His research focuses on developing disease and pest-resistant rootstocks, as well as breeding tables, raisin and wine grapes with resistance to Pierce’s disease and powdery mildew.


ALEXA: So Amy, I discovered that there's someone here on campus that I feel is a little bit of a hero.

AMY: Me, right? No?

ALEXA: No...

AMY: No?

ALEXA: No. Maybe you're second, maybe even third after Gunrock.

AMY: Oh.

ALEXA: But I'll give you a hint, he's really into grapevines.

ANDY: Grapevines are unbelievably amazing plants that grow in a peculiar environment. They're usually very ambitious and aggressive plants in many ways because they have to survive in a forested environment and grow through the canopy very quickly. But it changes them completely. Once you think about them as a wild plant, you realize the flaws we're making in terms of growing them as a cultivated plant. They're fighting us every step of the way and we're fighting back I guess with things that they don't appreciate.

ALEXA: Do kind of see where I'm going with this? Like, can you guess?

AMY: Just introduce him already, Alexa.

ALEXA: Alright. Well, that's Andy Walker and he's a grape geneticist and a grape breeder at UC Davis, so he spends a lot of time with the vines that he just described. Andy's working to keep wine safe from its top villains. So like I said, he's a hero.

AMY: I get it. You know it is interesting to think of a plant that produces such a lucrative fruit as being sort of weed-like like he said but grapevines are kind of like that.

ALEXA: They can even survive fire sometimes. But they do have an enemy, which is where Andy comes in as protection.

AMY: For your favorite beverage, right?

ALEXA: Well hey, someone has to make sure that our glasses stay full.


ALEXA: I'm Alexa Renee.

AMY: And I'm Amy Quinton.

ALEXA: And it's time for a Bonus Bite. In this episode, we're talking about the future of wine with Andy Walker.

ALEXA: Before we met Andy, Texas, and wine- those two things never really paired up in my head. But he told us that he goes out to Texas to hunt for wild grapevines.

AMY: He's trying to breed grapevine varieties that are more resistant to pests and diseases to keep our vineyards here in California healthy.

ALEXA: And we learned Texas happens to be a great place to find new grape varieties to breed.

ANDY: Texas has about- anywhere from eight to twelve or fifteen different grape species there. And they have resistance to a lot of pests and diseases, a lot of climatic adaptation. There's a fairly wide range of climates they grow in. So I wander around looking for them all.

AMY: I can just picture him stopping by a lone Texas hill country highway looking for grapevines. He told us that the highway department down there is just killing these wild plants because like Andy said, they grow like weeds, but he wants to save them so they don't disappear forever.

ANDY: So I've been collecting them. We have twelve hundred different genotypes I've collected across the southwest now here on campus. And I'm not sure if they're very useful but was a lot of fun collecting them. They're sort of my contribution to the future. People can use these materials and find the resistances they need and hopefully create something better with them.

ALEXA: One of Andy's goals is to breed grapes that are resistant to Pierce's Disease, which can devastate a grapevine pretty quickly despite it being a resilient plant.

AMY: So let's explain Pierce's Disease.

ALEXA: Simply put, it's a bacterium that here in California is spread from one vine to another by a type of leafhopper insect known as the glassy-winged sharpshooter. The bacteria block the vine's water flow and eventually just kills the plant.

AMY: I always picture this like, bug with like, some pistols on its side like the sharpshooters.

ALEXA: It does sound something like that.

AMY: And when the climate gets warmer Pierce's Disease could spread up to northern regions of the state since the sharpshooter also likes warm weather.

ALEXA: Andy hopes he can develop grapevine rootstocks with traits that can adapt to the effects of climate change, particularly here in California. Effects such as warmer temperatures and more severe droughts, which can make the soil salty, are all big issues for wine.

AMY: But here's the thing about wild grapevines in Texas...

ALEXA: Grapes that grew on them, well...

ANDY: Most of them taste terrible.

AMY: Andy's challenge is to find and breed tolerant and resistant grape varieties that also taste good.

ANDY: The reason that the all the wines in the world are made from Vitis vinifera, which is the European wine grape, is because it's very tasty compared to all the other species. There are many species alternatives, but they have tremendous flaws in terms of acidity high- very high acidity, very bitter astringent flavors, highly tannick. Oftentimes too red in a sense. Almost black-red instead of purple-red.

ALEXA: Not something we want in our wine glass. So Andy and other grape breeders cross the tasty vinifera species with a not-so-tasty resistant species. They do this over and over again, basically selecting the best materials and the most highly resistant materials until they make a good wine!

AMY: And they eventually dilute out the harsh taste that way.

ANDY: It's not a highly recognized way of producing better wine grapes. It's a highly recognized way of producing more disease resistant wine grapes that can compete or at least stand on the same ground as traditional wine varieties.

AMY: Taste is subjective though.

ALEXA: Yeah and apparently millennials have a different taste for wine. Like when I go to the grocery store and I'm shopping for wine I see wines and like to-go cans, I see them in juice boxes- they're pretty much made for picnics.

AMY: Yeah. I'm Gen-X, I prefer my wine in a bottle or a glass.

ALEXA: I'll take either. But I have read that millennials, like myself, we could actually help save wine and Andy actually back me up with this.

ANDY: I think you're right in terms of millennial taste buds or they're perhaps different. We should market that as breeders and focus are our ability on creating wider markets for different varieties- new varieties.

AMY: Wait. Didn't you read that new state of the wine industry report from 2019?


AMY: Well, some kind of wine fan you are. The latest is that millennials are not living up to expectations. They are not buying as much wine as expected.

ALEXA: We millennials, we just get blamed for everything!

AMY: Well then, let's blame the Baby Boomers because you know what? They're currently leading the sales but they're about to head into retirement. Their income is going to be limited, their contribution to wine sales are expected to decline and millennials have not caught up partly because well, they're poor and they legalized cannabis.

ALEXA: That sounds about right. What you're basically saying is the wine industry should target Gen-X.

AMY: Correct.

AMY: Okay, Alexa. I know you like traditional sort of ancient varieties of wine like cabernet sauvignon but are you willing to try something completely different?

ALEXA: I'm willing to try anything that will keep wine thriving. I may even try that Moroccan or Greek wine variety that Andy mentioned when we visited him. He did encourage us to get out there and expand our taste buds.

ANDY: There's not a lot of interest in new varieties and new types. There's interest in new wine styles and I think it's a golden opportunity now to convince a new wine drinking public that both are not incompatible. That we can have other varieties and different wine styles at the same time by choosing different varieties. Also, it will give us a far greater chance of addressing climate change issues, addressing disease issues and really doing it in a more sustainable and long-term fashion too.

AMY: But we can't just rely on folks like Andy to save wine.

ALEXA: No. But the good news is, wine grape growers are already starting to make adjustments to high temperatures and later, if necessary, Andy did tell us that varieties from hotter, drier parts of the world can eventually be grown here in California if the heat stress becomes too much.

AMY: So the experts are working on it.

ALEXA: And as consumers, we should too.

AMY: Thanks for listening.