2018 Falling Numbers Data for Winter Wheat WSU Variety Testing Trials

The Hagberg-Perten falling number (FN) test measures starch digestion by the enzyme alpha-amylase. Lower FN indicates the presence of more alpha-amylase, which can lead to problems with poor baking quality. Customers who purchase Washington wheat generally require a FN over 300 seconds. Thus, farmers can receive discounts for wheat with FN below 300. There are two causes of low FN, LMA due to a cold temperature shock during grain filling and preharvest sprouting when mature wheat experiences rain. The winter wheat experienced a potentially LMA-inducing cold shock in June.

The first step in our falling numbers testing process is to perform a survey of 4 to 10 varieties known to have problems with low falling numbers at every location. We use this information to determine which locations should have FN tests run on all entries. However, the soft white winter survey that has just been completed painted an interesting picture of the 23 soft white winter wheat variety trials locations.

The map in Figure 1 tells us that there are while there were a fair number of locations with FN below 300, most of these locations were above an FN of 250. There were 8 locations with either FN at or above 300 (green) or over 280 (light green). So these locations likely did not have a serious low FN problem. There were 8 locations with FN between 250 and 300 (yellow), 3 locations with only one susceptible line showing FN below 250 (orange). Finally, there were only two locations with multiple lines below FN 250 (red), Dusty and Ritzville. In 2016, there were 12 soft white winter locations with multiple lines show FN below 250.

Falling number data from these two worst locations, Dusty and Ritzville, may help identify varieties resistant to low FN due to LMA from the cold shock.  So the falling numbers for the complete variety trials in Dusty and Ritzville have been posted on the PNW Falling number website.  The hard winter variety trial falling numbers are also available for Ritzville. More locations will be added once we have completed FN-testing of all entries, not just the highly susceptible ones.

Keep in mind that the information on the map is from a survey of ONLY susceptible varieties. This map does not represent the actual FN of farmers’ wheat. It shows us where there may have been potential for low FN in susceptible varieties due to LMA-inducing cold temperatures in June. Also remember, LMA-inducing conditions are dependent on the timing of weather events to plant development, so there can be a great deal of variation on a single farm. So look at 2014 and 2016 data to get a fuller picture of each variety. We will learn more about the impact of LMA as the 2018 harvest season continues.

The USDA-ARS Steber lab and Washington State University (WSU) collaborators have evaluated falling numbers (FN) in the WSU variety trials since 2013.

Figure 1
Survey map of low FN in inland Washington state.
(Select photo to enlarge)

For questions or comments, contact Camille Steber via email at camille.steber@ars.usda.gov.

Washington State University