California is a national and global powerhouse when it comes to nuts. Recent data shows that the Golden State produces roughly 80% of the world's almonds and 60% of the world's pistachios.
It's a lot of nuts and a lot of money. But changing climate conditions are challenging nut growers. With warming winters and a propensity for drought, crops that did well 20 years ago might not make it 20 years from now.
That's where the plant geneticists and breeders at UC Davis' Wolfskill Experimental Orchard come in. This week, Gabriela Glueck, KCRW's Julia Child Foundation Reporting Fellow, takes us on a trip to the orchard to meet with two nut crop breeders who are trying to set up California almond and pistachio growers for success.
Gabriela Glueck: The olive trees were the first thing I noticed, thick trunked with silvery green leaves, perfectly pruned, lining either side of the entrance road. Beyond them lay the rest of the orchard. From where I parked my car, I could see pomelos, pistachios, grapes, kumquats, and a massive cactus sprouting prickly pears. The Wolfskill Experimental Orchard definitely feels like an experimental orchard. It even has a designated "Torture Orchard," where researchers push plants to their limits to see what they can take. Tucked away in the western Sacramento Valley, near Winters, California, it's a scientific playground for plant breeders like Tom Gradziel.
Thomas Gradziel: I'm a geneticist plant breeder at the University of California at Davis. The aspect of plant-breeding involves both generating new varieties as well as testing them long-term, multiple decades, over many different locations.
Gabriela Glueck: Tom has been at Wolfskill for more than 30 years. He's part of a legacy dating back to the 1930s when the land was gifted to UC Davis by the Wolfskill family. John R. Wolfskill was a California rancher, and he set up shop here in 1842. He was also a horticulturist at heart, bringing with him a collection of fruit seeds and cuttings from around the world. The olive trees at the entrance? He planted those. Since then, work at Wolfskill has resulted in the development and release of 55 new crop varieties. It's all part of a mission to cultivate resilient crops. Tom is focused on almonds and peaches.
Thomas Gradziel: So we're looking at a block of probably 3,000 trees. These are all seedling trees. So these are all progeny from crosses within the breeding program.
Work at Wolfskill has resulted in the development and release of 55 new crop varieties. Plant breeder Tom Gradziel focuses on almonds and peaches. Photo by Gabriela Glueck.
Gabriela Glueck: When it comes to plant breeding, his approach is both scientific and poetic. If you ask him to explain the basics, he's quick to paraphrase Tolstoy.
Thomas Gradziel: Anna Karenina, the first line is, all happy families are alike, all unhappy families are not alike in different ways.
Gabriela Glueck: For Tom, that's how he sees plant-breeding. When things go right, you get yourself a perfect fruit. When they go wrong, well, there could be a million reasons why.
Thomas Gradziel: You know, over here we see this tree with a wonderful crop. There's a lot of desirable traits that are easy to see. What wrecks a relationship are these undesirable traits that reach a threshold to say this is no longer tolerable. I'm not talking dating game anymore. I'm talking about tree crops.
Gabriela Glueck: Tom's looking to breed almonds that can take what California is dishing out. Less winter chill, more drought and more heat.
Thomas Gradziel: These are the types of unknowns that we're looking at.
Gabriela Glueck: Consider the nonpareil. Nearly 40% of all almonds produced in California are nonpareils. They're a productive variety in high demand. Their mild sweetness has come to define a California almond. But, they're not perfect. One problem? Nonpareils need pollen from other varieties of almond trees to fertilize their flowers.
Thomas Gradziel: Its genetics tells it to not accept its own pollen, because its genetics has evolved to say we don't want to be inbred.
Gabriela Glueck: Farmers who grow nonpareils have to plant pollinator trees in the same orchard. Warmer winters have thrown these companion varieties out of sync, meaning they aren't blooming at the same time. Tom's working to breed a solution, a pollinator tree that doesn't need as much winter hibernation to bloom. And then there's the issue with the pollination process itself.
Thomas Gradziel: We need the honey bees to move that pollen. You may be aware that this year, the honey bees, we are seeing another possible major collapse in hives.
Gabriela Glueck: This has made many almond growers interested in self-pollinating trees. That's another research project on Tom's already long to-do list. But breeding new almond varieties takes time, about three to five years for a newly planted tree to even yield its first crop. Then comes years of observation. As Tom likes to put it, as with many relationships, the undesirable characteristics aren't always evident on day one. While farmers can't afford to make this kind of gamble, planting acres of a new variety just to see what happens, Tom and other breeders at Wolfskill can.
Thomas Gradziel: We want to test those trees in environments that if they have a bad trait, it's more likely to show. We don't want to pamper them. We don't want to give them everything that they need. We don't want to, for instance, put a lot of fungicides for disease control or pesticides for insect control, because if they have a strong susceptibility, we want to see it and we want to take those out, eliminate them.
Pat Brown, a pistachio and walnut breeder, got a grant to look at water stress in pistachios. So he set up shop in the "Torture Orchard." Photo by Gabriela Glueck.
Gabriela Glueck: Researchers here are playing the long game, asking questions like, what happens if we skip a day of watering, reduce water or turn off the tap entirely? That's how you learn things. Remember the "Torture Orchard?" That's where this kind of experiment happens. A few years back, Tom's colleague, Pat Brown, a pistachio and walnut breeder, got a grant to look at water stress in pistachios. So he set up shop in the "Torture Orchard."
Pat Brown: We had these trees, so we wanted to withhold water until some of them started to die. We wanted to see which ones lived and which ones died.
Gabriela Glueck: To Pat's surprise, all the pistachio trees survived. They even made it through their next trial: salt water.
Pat Brown: There we did see pretty pronounced differences between the plants. So some of the plants dropped all their leaves and essentially looked dead, although most of them sort of came back to life, and some of them looked fine.
Gabriela Glueck: With freshwater a limited resource, the idea that growers might be able to pull from saltier sources is a big win. For Pat, his "Torture Orchard" experiments are an attempt to pinpoint pistachios strengths and weaknesses. If he can identify a vulnerability, he can try to solve for it. Breeding nuts that can handle less winter chill is also high on his list. For Pat, and many breeders at Wolfskill, finding solutions can often mean pulling plant genetics from around the world.
Pat Brown: So we're standing pretty close to the pistachio germplasm repository here, which has pistachio trees from all around the world, including the Mediterranean and even into North Africa, which has basically no chill at all.
Gabriela Glueck: Pat's referencing the USDA National Clonal Germplasm Repository. It’s basically a massive library for plant genes. It allows breeders to access genetic material from around the world without ever leaving the Orchard. It’s one of the many perks of working at Wolfskill. And for California’s nut breeders and growers, it’s a welcome advantage for an uncertain future.