By Seth Truscott, College of Agricultural, Human & Natural Resource Sciences
PULLMAN, Wash. – Washington wheat farmers are being hit hard by low falling numbers in their grain. A sign of poor flour quality, low falling numbers are caused by severe temperature swings or rain before harvest.
To help growers recover, researchers at Washington State University, funded largely by farmers through the Washington Grain Commission, are developing information tools and better varieties, ensuring higher-quality yields in future.
Since 2013, the commission has funded Camille Steber, a U.S. Department of Agriculture wheat geneticist, and other researchers at WSU to screen varieties for susceptibility to low falling numbers. Results of this project, including a database of variety susceptibility across regions, are available online at http://steberlab.org/project7599.php.
Numbers fall statewide
Steber has watched Northwest wheat and weather for months. Rain and temperature swings in July sparked her worries. When test results came in at early harvest, she knew there was a problem.
“My lab has run falling numbers on eight WSU cereal variety testing locations and we’ve seen low numbers from all eight—all drier places,” Steber said. “That’s bad. That means the problem is widespread.”
Northwest wheat growers experienced problems with low falling numbers in 2011 and 2013, with pockets of low numbers the last two years. The summer of 2016 is shaping up to be worse.
“We don’t have hard numbers yet, but are concerned that a higher than normal percentage of the wheat crop could be below industry standard,” said Mike Pumphrey, WSU spring wheat breeder and geneticist.
Low falling numbers have been found in winter wheat, which is harvested first, but “we expect both winter and spring wheat will be affected,” said Pumphrey. “Conditions that bring low falling numbers have affected both crops.”
What causes low falling numbers?
The term “low falling number” comes from a gravity test that measures starch damage in flour caused by alpha-amylase, an enzyme that affects baking quality. Flour with too much alpha-amylase means crumbly, gummy bread and cakes that fail to rise.
Alpha-amylase is produced when grain sprouts. When too much rain falls at harvest, grain can sprout on the stalk, turning starch into fuel for growth.
Low falling numbers also happen in non-sprouted grain, in a form called late-maturity alpha-amylase, or LMA, caused by temperature shocks during maturation. The Northwest saw exactly those conditions in late June and early July.
“We had a massive yo-yo,” said Pumphrey. “We saw severe temperature spikes of up to 95 degrees throughout the region, followed by 40-degree nighttime lows that persisted for days during a critical period. That’s the textbook condition for expressing LMA. We couldn’t have done any better in our labs.”
While farmers are mostly done harvesting in central Washington, much wheat remains to be cut in the north, south and east.
Harvest quickly to reduce damage
To reduce the chance of sprout damage, Steber urges farmers to harvest wheat quickly after maturity. Once wheat is sprouted, there’s little that can be done for quality.
Some evidence suggests that if wheat is stored for a time, falling numbers could rise as the enzyme degrades – but this only works if the falling numbers are not below 200.
“You’re going to see local elevators and individual farmers storing their wheat and hoping that it climbs enough to get across the threshold of 300,” said Pumphrey.
Washington Grain Commission CEO Glen Squires said the commission has initiated discussion with U.S. wheat associates and overseas markets regarding potential for utilizing wheat with a falling number lower than 300.
New information tools
Safeguarding against low falling numbers is one of Pumphrey’s primary breeding goals. Likewise, Steber is working with other WSU researchers, including winter wheat breeder Arron Carter and USDA-ARS club wheat breeder Kim Garland-Campbell, on selection of wheat with better resistance to LMA and sprout.
“We have been screening advanced lines and new releases the past three years to make sure they’re much less likely to have this problem,” said Pumphrey. “Breeding the perfect wheat isn’t easy. But we have good, adapted wheat varieties with stable falling numbers.”
WSU researchers know that some varieties of wheat hold up better than others to sprout or LMA. WSU Extension’s goal is to create a list of varieties, site by site, that are susceptible to low falling numbers and should not be planted. Researchers will also step up analysis of new varieties not included in previous data, and investigate the weather connection using data from the university’s AgWeatherNet stations.
“We know the cause, but there are still some mysteries,” said Ryan Higginbotham, a cereal variety testing specialist with WSU Extension. “We don’t want to steer growers away from potential good fits. We want to present data in a way that makes sense.”
Results will be available at WSU variety field days, the WSU Extension small grains website and in its online variety selection tools.
“Timing, variety selection and luck are all factors,” said Pumphrey. “That’s why I ask growers to consider planting multiple varieties with contrasting traits like maturity, so they can spread their risk.”
“If farmers want to manage risk, we want to give them the tools,” Higginbotham said.
• Read about WSU variety selection and testing at http://smallgrains.wsu.edu/variety/.
Camille Steber, USDA-ARS Molecular Geneticist, WSU Assistant Professor (Adjunct) of Crop and Soil Sciences, (509) 335-2887, firstname.lastname@example.org
Ryan Higginbotham, Regional Specialist, WSU Extension Agriculture and Natural Resources, (509) 335-1205, email@example.com
Mike Pumphrey, WSU Spring Wheat Breeder and Geneticist, Associate Professor and Endowed Chair, Crop and Soil Sciences, (509) 335-0509, firstname.lastname@example.org