As the Plunger Falls: A Discussion on Low Falling Numbers with Kim Garland-Campbell and Camille Steber


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Show Notes & Resources Mentioned:

Part Two is now live.

Contact Information:

Contact Camille Steber via email at and contact Kim Garland-Campbell via email at

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Episode Transcription:

Drew Lyon: Hello. Welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat podcast do us a favor and subscribe on iTunes or your favorite podcasting app and leave us a review while you’re there so others can find the show too.

[ Music ]

Drew Lyon: Welcome to the first of two episodes on low falling numbers with Kim Garland-Campbell and Camille Steber. Kim and Camille are both research geneticists with the USDA-ARS, with adjunct faculty appointments in the WSU department of crop and soil sciences in Pullman. Kim has been a wheat breeder since 1992, and has been in her current position since 1999. The goals of her project are pre-breeding for wheat disease resistance, and club wheat cultivar development. She has the distinction of being the only wheat breeder who has a primary focus on club wheat. Camille obtained her Ph.D. from the University of Chicago in molecular genetics. She did her post-doctoral work on seed germination at the University of Toronto. She has been with the USDA-ARS for 21 years, working on seed germination, pre-harvest sprouting, and the falling numbers problem in wheat. Hello, Kim.

Kim Garland-Campbell: Hello. How are you, Drew?

Drew Lyon: Doing well. And Camille, welcome.

Camille Steber: Thank you.

Drew Lyon: So how did the two of you wind up working on falling numbers?

Camille Steber: Actually, Kim and I have been working on pre-harvest sprouting pretty much the entire time we’ve been working for the USDA, and pre-harvest sprouting is one of the major causes of low falling numbers. So we started having problems with low falling numbers in 2011 and 2013. We were called on to start working on this problem. That was when we became interested in falling numbers per se —

Kim Garland-Campbell: Right.

Camille Steber — as opposed to seed germination.

Drew Lyon: Okay. So falling numbers — a lot of people may wonder, what the heck is falling numbers? What is the falling numbers test, and why is it used in the wheat industry?

Kim Garland-Campbell: Well, it is a test where, basically, what is done in the machine is wheat flour is mixed with water and then heated up to make a slurry. And essentially, what the machine does is make gravy, and then a metal rod is dropped down through the slurry, and the falling number refers to the amount of time in seconds that it takes for that rod to fall through the slurry and hit the bottom. And so, 300 seconds is the minimum specification that a lot of our import customers require, so that would be, what, five minutes? Yeah. I’m doing math in my head [laughter from Drew and Camille], so five minutes is — and anything below that receives discounts at the elevator because they know they’re going to have more of a problem to market that wheat.

Drew Lyon: Okay, so if the plunger falls faster, the gravy is thinner?

Kim Garland-Campbell: Right, yeah.

Drew Lyon: And how does that translate into what the marketplace is looking for?

Camille Steber: So, I mean, the point of the falling numbers machine — it’s an old-fashioned way of measuring the presence of the enzyme alpha-amylase in the wheat flour.

Drew Lyon: Okay.

Camille Steber: And alpha-amylase is an enzyme that digests starch. If the starch gets digested into smaller, shorter starch chains, it reduces its gelling capacity, and that can translate into problems with poor end product quality — so cakes that fall, or sticky noodles, or sticky bread. I mean, even before you get to the problem where you would have bread that doesn’t rise well, what they find is that when it goes through the factory, and they have big slicing machines — if there is any pre-harvest sprouting or problems with low falling numbers, there’s a risk that the slicing machine will get gummed up.

Drew Lyon: Oh, okay.

Camille Steber: And it costs them a great deal of money to stop the line and clean the slicing machine, so they really don’t want to see any risk at all that they have too much alpha-amylase in their flour that can gum up the works.

Drew Lyon: Okay. So what I guess this alpha-amylase causes is the reason we have low falling numbers. Can you talk a little bit more about why we have alpha-amylase problems, or is — I mean, is it something that shouldn’t be there, or is it something that’s — explain it a little bit [Drew laughs].

Camille Steber: Well, the reason you get alpha-amylase production during pre-harvest sprouting is that it’s a necessary part of seed germination. The whole reason that wheat grain is good food is because it has that nice, starchy endosperm that we turn into flour. That starch is there because mother plant has left it there as a way to feed the growing seedling as it germinates.

Drew Lyon: Okay.

Camille Steber: So you don’t want to, for example, make a genetically-modified wheat that has no alpha-amylase, because you’d get very poor emergence, because there’d be no way to fuel the growth of the seedling before it starts to do photosynthesis, after it start — after it clears the soil. So we can’t take a “just get rid of all of it” kind of approach. We need to have the alpha-amylase present when we plant our crop. We just don’t want it to be present prematurely if germination is initiated when the crop gets rained on before harvest. There’s another cause of alpha-amylase in the grain, and that one is more developmental. If we have a big temperature fluctuation during the soft dough stage, late soft dough stage of grain filling, you can get induction of alpha-amylase in the grain, which then causes you problems with low falling number.

Drew Lyon: Okay. So the two of you have been —

Camille Steber: Oh, I should’ve said — and that problem is called late-maturity alpha-amylase, or LMA.

Drew Lyon: — Okay, so we have this pre-harvest sprouting and late-maturity alpha-amylase, two different issues, but basically causing a similar problem, this low falling numbers affecting quality of whatever product we’re going to — after it. So both of you have been, as you said, working on low falling numbers for a long part of your career, but I know these incidences — 2011, 2013 have really spurred the industry to want some answers, and you two have responded to that. So can you tell me some of the things you’re finding in your research, some of the good news, bad news kind of information?

Kim Garland-Campbell: Well, I think the good news is, I just recently looked at all of the data that Camille has collected since 2013 for our major market classes, which would be the hard red spring, the hard red winter, soft spring, soft white spring, and soft white winter, and by and large, most of the cultivars that we analyzed have some resistance to low falling numbers, and some are very good. Unfortunately, though, some are very bad, but at a low percentage. But the other unfortunate part is, they’re the ones that are the most widely grown [laughter], so —

Drew Lyon: Interesting.

Kim Garland-Campbell: — Especially in the soft white winters, some of the lines like Curiosity CL+ and Bruehl Club wheat are among our worst performers. And we think that there’s a connection between the propensity for low falling numbers and the emergence trait that those cultivars were bred for, where, you know, they have to be planted very deep and emerges very, very fast to get up out of the ground. So that’s the bad news.

Camille Steber: Yeah. So the alpha-amylase is the thing that fuels seedling growth, so it’s the thing that fuels emergence.

Kim Garland-Campbell: Right.

Drew Lyon: Okay. So it’s — that’s good. The plant wants that —

Kim Garland-Campbell: Yeah. Right.

Drew Lyon: — to grow, but then it’s — and yield.

Kim Garland-Campbell: Yeah. Right.

Drew Lyon: And yet, it’s bad when it comes to —

Kim Garland-Campbell: It comes at the wrong time. Like, you know — so if we get these temperature fluctuations, or rain at harvest, those particular lines are more liable to have low falling number problems. So — you know, and it isn’t — it isn’t really part of the class. Every class has this, has good and bad lines — mostly good, but some bad [laughter], and that includes club wheat. Like Bruehl is one of our worst lines, and Crescent is one of our best lines. So it’s not a class thing. It’s just the genes segregating within —

Drew Lyon: — okay. So I know I’ve talked to Clark Neely, our Variety Testing person, and I think you’re trying to figure out how to get that information into the variety testing —

Kim Garland-Campbell: — right, yeah.

Drew Lyon: — information that’s found on the small grains website. Where are you at on that?

Kim Garland-Campbell: Well, actually, I had told them I’d have it to them by last week, but then I went out of town [laughter]. So now, yesterday, I said, “Okay, by Friday.” You know, so I should have the data analysis to him by the end of the day tomorrow, and then, you know, he’ll probably have to format it a little bit. But we should be able to get it up pretty quick.

Drew Lyon:So growers will be able to take a look at the varieties and see how they —

Kim Garland-Campbell: Right, how they rank, yeah.

Drew Lyon: — how they rank for that.

Camille Steber: Yeah, because we now have, you know, data — falling numbers data on the variety trials, going all the way back to 2013 on the falling numbers website on, and Kim is integrating all of that data together in order to give you a summary of how those varieties behave across all of those years and environments.

Kim Garland-Campbell: Mm-hmm.

Drew Lyon: So is it going to be a — do you have an idea whether it’s going to be a numbers system, or a good, bad, very good type thing?

Kim Garland-Campbell: I think what we’re — yeah, what we’re aiming for is the one to 10 scale that we’ve used for all the other traits. So one would be good, and 10 would be bad.

Drew Lyon: Okay.

Kim Garland-Campbell: And though — down — right now, we’re just going to put it up, like okay, of all the environments that had an issue, these varieties, you know, performed well. These varieties didn’t perform well. And then, down the road, we’re going to refine it a bit, and separate out whether it’s for pre-harvest sprouting or LMA conditions.

Drew Lyon: Okay.

Kim Garland-Campbell: But we figured right now, let’s just get it up there, and then —

Drew Lyon: Okay. So this is low falling numbers in general.

Kim Garland-Campbell: — right, in general, yeah. Yeah, and we just met — I think it was two weeks ago, with the folks from Ag Weather Net to do some work. I don’t know that you know this, Camille, but —

Camille Steber: No.

Kim Garland-Campbell: — do some work with the weather data that they have collected over time to better define, like, what was the likely cause of the issue in the environments for all these data points that we have, going back to 2013. So — because we know if it rained, you know, they’re — if it — well, I guess I should say we know if it didn’t rain,and we had a low falling number problem, then it was LMA. If it did rain, it could be pre-harvest sprouting, or it could be both. And so,we want to separate those environments out.

Drew Lyon: And is there a — from a producer standpoint, or an end-user standpoint, is there a difference whether it was caused pre-harvest sprouting — whether the low falling numbers was caused pre-harvest sprouting, or whether it was caused by LMA?

Camille Steber: There’s evidence in the literature that LMA has a less profound effect on end use quality than pre-harvest sprouting does.

Drew Lyon: Oh, okay.

Camille Steber: But as Craig Morris likes to point out, those studies need to be done more carefully with real near-isogenic lines, so that you’re — you know you’re looking at a difference between pre-harvest sprouting and LMA, rather than a difference between variety X and variety Y.

Drew Lyon: Okay.

Camille Steber: But so far, it does seem like there’s a smoking gun in that pre-harvest sprouting has a more profound effect, and the — the reason for this is likely that LMA is a fairly specific induction of just the alpha-amylase enzyme, whereas in pre-harvest sprouting, you know, the starch isn’t the only thing that the seedling has to eat. There are also — there’s also fat, and there’s protein. So that germinating seed actually produces a whole suite of digestive enzymes, breaking down proteins and lipids, and that may also be having an effect on end-use quality, besides the really obvious problem that there’s expression of alpha-amylase.

Drew Lyon: Okay. Thank you both very much.

Kim Garland-Campbell: Thank you.

Camille Steber: Thank you, Drew.

[ Music ]

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcasting app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon — that’s –( You can find us online at and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.