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Above fields of wheat in northern Colorado, drones equipped with thermal imaging technology read the temperatures of swaying canopies.

They’re looking for wheat plants that stay cooler than the rest — a serious advantage as the world gets warmer.

Extreme heat and cold snaps are testing the resilience of plants globally. Droughts are threatening water reserves. Floods are devastating crops. Without intervention, climate change could threaten the global wheat supply.

Used to make breads, porridges, and alcoholic beverages, wheat provides the world with 20 percent of its total calorie intake. In developing countries, 1.2 billion people rely on wheat to survive, according to the International Maize and Wheat Improvement Center(CIMMYT), headquartered east of Mexico City.

One way to keep bread on the table, so to speak, is through plant breeding— cross-pollinating two varieties of a plant. The hope is that the offspring will have their parents’ most desirable genetic traits. For wheat, that means things like baking quality, disease resistance, and heat tolerance.

Esten Mason, associate professor and head of Colorado State University’s wheat breeding program, recalled a scorching two-week stretch in June. As temperatures hovered in the mid-90s in drought conditions, CSU’s wheat fields wilted, providing only about 50 bushels per acre compared to the usual 80.

That was bad news for farmers. But for breeders, it was an opportunity: If some plants performed better, they could be selected to breed new, more heat-tolerant plants.

“You're constantly responding and progressing,” said Mason. “That's the goal: To make progress every breeding cycle.”

CSU is about an hour and 20 minute drive north of Denver on the western edge of America’s breadbasket. Billowing from Texas up into the Canadian Prairies, the Great Plains is where North America grows most of its wheat.

Like all plants on Earth, wheat varieties have preferred environments. If the conditions are right, with ideal temperatures and rainfall, they’ll prosper.

If they aren't, wheat can be stunted, their grains may not grow as large, or they could die out entirely.

If the early part of the growing season is hot, plants can get "over-eager." They mature too quickly, and don't grow as tall as they should, explained Matthew Reynolds, the head of wheat physiology at CIMMYT. He said they focus on trying to grow quickly, putting leaf production on the sidelines, which leads to nutrient deficiencies.

With increasing droughts around the world, wheat plants need to be able to better access and budget water with deeper, and more efficient root systems.

“Imagine you've got a backpack full of water and you have to cross 20 kilometers of desert,” Reynolds said. “You have some strategy based on your experience, your body type, the time of year and so on. A plant can do that, the only problem is the plant is always going into a completely unknown season.”

Selecting wheat varieties with better root systems for drought-prone areas could boost yields.

To examine root structures in wheat, breeders peer beneath the soil with infrared technology, Reynolds said, which is faster than digging the plants up.

Nowadays, researchers can also look at a plant's DNA to see if certain traits are present, allowing them to better predict success.

In trials at CSU, harvests of an older wheat variety called Kharkof have been checked against new varieties to compare performances since the 1930s. The older line produces yields 50 to 75 percent lower than the new ones, Mason said.

Of the roughly 2 million acres of wheat grown in Colorado, 90 percent of it is composed of varieties developed at CSU, and more of them can be found sprouting up in other states.

“There was a wheat variety released out of the program called Byrdthat had an excellent drought tolerance,” Mason said, also noting its resistance to certain debilitating wheat diseases. “It had a big impact on wheat production in the state.”

Breeding for local conditions and issues is key. But wheat is a global enterprise. In many countries, companies and government institutions either aren’t putting the necessary resources into these efforts or simply don’t have the resources to spare.

Reynolds pointed at vulnerable areas around the Mediterranean, southern Africa, and pretty much anywhere around the equator. Droughts around the globe, including in Madagascar and Brazil, are drying crops and sapping water reserves.

“The water resource situation globally is not a good one,” he said. “And nor are many of the people who own small farms in the global south in a position to invest in sophisticated irrigation equipment.”

Organizations like CIMMYT work to create partnerships between growers, government agencies, research institutions, and private companies to spur effective breeding programs for staple foods where they’re needed most.

These challenges aren’t exclusive to wheat, either. Lots of plants that we use for food, fuel, and other materials are sensitive to climate change, and breeding them takes funding, training, and work.

“We’re living on a bit of a borrowed time,” Reynolds said. “It's time to move.”

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