MANHATTAN, KANSAS, U.S. — Kansas State University (KSU) scientists are testing more than 300 wheat cultivars under heat-controlled tents to show that high nighttime temperatures are negatively impacting the quantity and quality of the U.S. wheat crop.

“A small computer, called a Raspberry Pi, is used to monitor temperature and adjust conditions inside the tents so that the researchers can determine the cultivars that are less — and more — susceptible to high temperatures,” said Dan Wagner, a graduate student in computer science who built the system.

The researchers believe they are the first to build this type of heat-controlled facility.

“This is not just the wheat grown in Kansas,” said crop physiologist Krishna Jagadish, an associate professor of agronomy. “These lines represent the entire U.S. hard red winter wheat collection.”

There are eight sections of wheat, each split into 40 rows containing one wheat cultivar. It adds up to 320 wheat cultivars, many of them hard red winter wheat or their offshoots that are grown somewhere in the country.

The researchers have built six tents, each growing the same 320 cultivars but held under different environmental conditions. There is no facility like this in the world, Jagadish said, noting that the project will provide researchers with important data to help them generate newer wheat varieties with tolerance to heat.

“We will be harvesting each of the cultivars through the end of June,” said Raju Bheemanahalli, a post-doctoral fellow in KSU’s Department of Agronomy. “Then we will analyze the size and number of grains, protein content and more. From that, we will identify the genomic regions that will help in developing markers controlling heat tolerance.”

Eventually, he said, those markers can be used by wheat breeders to develop varieties that yield well even under more intense heat.

KSU noted that regardless of where wheat is grown, it is susceptible to heat, and researchers now believe that high nighttime temperatures can be equally damaging as high daytime temperatures.

The tents that KSU built are designed to expose wheat to typical field conditions while comparing it closely to wheat grown under more controlled conditions.

“We have three control tents in which we don’t roll the side walls and end walls down so that we let fresh air in,” said Nathan Hein, an assistant scientist in K-State’s Department of Agronomy. “And then we have three heated tents that we completely shut down overnight.”

The heated tents are kept at a temperature 4 degrees Celsius above the outdoor temperature. Six sensors inside each tent are located to make sure the temperature is held uniformly across the 320 wheat cultivars.

“The Pi (computer) operates like a thermostat in your house,” Hein said. “Once the temperature drops too low, it flips the relay and turns the heater on. When the tent’s temperature is 4 degrees Celsius above the outside temperature, then the Pi shuts the heaters down.”

Jagadish said that causing stress uniformly to the cultivars in a common setting provides valuable clues to which ones will perform better in actual field conditions.

“We may find that specific lines coming from a region are more susceptible to heat, and that the quality of the wheat gets even worse as nighttime temperatures increase,” he said.

The researchers have been studying the effect of nighttime temperatures for more than a year, first in a smaller pilot project and now in a more expanded, fully operational facility. Jagadish said it’s clear that high nighttime temperatures cause a deterioration in the wheat crop; the key is to minimize the damage.

“When exposed to high nighttime temperatures during grain filling, the grain weight, yield and starch content goes down, and the protein content increases,” Jagadish said. “That changes the dynamics of what is required for maintaining the quality of bread, including the elasticity, and qualities like that. High level of protein with increasing nighttime temperature will make the bread crusty, which means that you may not get the loaf of bread as you really like it.”