All About Alpha-amylase & Low Falling Numbers with Camille Steber

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Show Notes & Resources Mentioned:

Contact Information:

Contact Camille Steber by email at csteber@wsu.edu or by phone at 509-335-2887.


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Episode Transcription:

[ Music ]

Drew Lyon: Hello, and 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. We have weekly discussions 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: My guest today is Camille Steber. Camille is a U.S department of agriculture scientist with the agricultural research service. She has an edge on faculty appointment with the Department of Crop and Soil Sciences at Washington State University. She obtained her Ph.D. from the University of Chicago in molecular genetics and then she did her post-doctoral work on seed germination at the University of Toronto. She has been with the USDA-ARS for 20 years working on seed germination, pre-harvest sprouting and the falling numbers problem in wheat. Hello Camille.

Camille Steber: Hello Drew.

Drew Lyon: So, falling numbers, we hear a lot about that. A little more in some years than others. [Camille chuckles] This year we’re hearing it a bit more. Tell us a little bit about falling numbers and what’s the falling numbers test that people always referring to.

Camille Steber: The falling numbers test is designed to detect the presence of alpha-amylase, an enzyme in wheat grain, basically by making gravy out of the flour.

Drew Lyon: Okay.

Camille Steber: And so, if you have this enzyme alpha-amylase in your wheat grain, it will digest starch into sugars or shorter starch chains and when the starch gets digested like that, it loses its ability to gel when you make gravy. So, the inability to make gravy is an indicator that you’re going to have problems with poor end-use quality, cakes that fall, bread that doesn’t rise properly or sticky noodles. Because of this, our customers abroad are very interested in the falling number. They will only accept wheat with falling numbers above 300 seconds. So, we don’t want our numbers to fall too far.

Drew Lyon: So, we don’t call it the alpha-amylase test, we call it the falling numbers test and that’s, explain a little bit why it’s called “falling numbers”. That’s, I think some people. It’s an indirect measure, but people, if you don’t understand how it’s done, they might not understand quite why, why that name came up.

Camille Steber: [chuckles] It’s, uh, so, when the machine mixes gravy by moving a stirrer up and down in a slurry of water and flour and after it has stirred for 60 seconds, it drops the stirrer and it measures how much time it takes the stirrer to fall through the gravy. And if it takes more than, less than 300 seconds to fall, then you have an unacceptable amount of starch digestion.

Drew Lyon: Okay.

Camille Steber: And our customers really feel that that’s a good indicator for them of whether or not they are going to have problems with poor baking quality.

Drew Lyon: Okay. There are a number of tests done to look at baking quality. Why did you get interested in the falling numbers test?

Camille Steber: Oh, I actually started off with an interest in seed germination and preharvest sprouting, but it turns out that preharvest sprouting is one way that you wind up with alpha-amylase in your grain. And so, I, when we first started having problems with low falling numbers in 2011, Arron Carter and Michael Pumphrey, the two WSU wheat breeders asked me if I would collaborate with them on a project looking at breeding for higher falling numbers and that was how this whole crazy business got started [chuckles].

Drew Lyon: So, breeding for high falling numbers is basically breeding for low alpha-amylase or just?

Camille Steber: Yes.

Drew Lyon: Okay.

Both: They’re inversely related.

Drew Lyon: Okay. Very good.

Camille Steber: And there are two causes of low falling numbers. The one I started off looking at was preharvest sprouting. So, preharvest sprouting is, you know, simply germination. If the wheat, if mature wheat gets rained on and it doesn’t have enough starting seed dormancy, it will begin to germinate on the mother plant and producing alpha-amylase to digest the starch. And this is just a natural part of seed germination. That starch is there in the seed in order to act as a fuel source for seedling growth.

Drew Lyon: Right.

Camille Steber: So, we like having our alpha amylase when we first plant our seeds. For example, if you plant your seeds deeply, you need that alpha-amylase there so that the seedling can use the endosperm to fuel its growth so that it can clear the soil, you know, grow long, clear the soil before it can start doing photosynthesis after it gets out into the sun. But, it’s a problem if it happens at harvest time when we want to send it off to be turned into baked goods.

Drew Lyon: Okay. So, it’s a can’t be that you just get rid of it or you would have a seed that would never germinate.

Camille Steber: Or it would germinate but the seedling wouldn’t grow very well if it didn’t have artificial light supplied or sunlight supplied. And since we like to plant our wheat deeply, especially in the dry part of the state, we need that fuel source for our seedlings.

Drew Lyon: So, it’s kind of a fine-tuning. You want it but only at the right time.

Camille Steber: That’s just what biology is like [chuckles].

Drew Lyon: Okay. You say you got started with preharvest sprouting, but you’ve moved on from there. What are some of the other issues?

Camille Steber: This new can of wars called late maturity alpha-amylase. So, the problems that we had with low falling numbers in 2011 and 2013 were mostly preharvest sprouting, but we started realizing that some people were having low falling numbers problems that wasn’t really associated with rainfall. One farmer in particular, Brian Cockran sent me his SY Ovation in 2013 and said, “look, I’ve got my rainfall records. I don’t understand why this stuff has low falling numbers.” And when we looked at the distribution of alpha-amylase in that grain, we realized that Brian was having trouble with something called LMA, the production of alpha-amylase not during germination but during grain filling, during development. So, at the moment LMA is considered to be a developmental defect resulting in alpha-amylase deposition during grain filling when instead of converting starch into sugar, you should be turning sugar into starch.

Drew Lyon: Okay.

Camille Steber: So, it all started there and then we started, we saw more LMA problems in 2014 and then 2016, you know, it just, it was an enormous problem actually with LMA. We did have rain in some places, so I thought we were looking at preharvest sprouting initially, but when we did further testing, we realized that we were seeing problems with LMA and this year we had trouble with LMA without preharvest sprouting.

Drew Lyon: Okay.

Camille Steber: So, the problem this year was entirely LMA. And so, we’ve been doing falling numbers testing in the variety trials and posting it on the web. This means that the soft, white winter and hard winter variety trials this year are very good indicators of LMA resistance when you find the ones that have higher falling numbers. So, farmers might want to take a look at our website where we post the variety trial information. It’s on steberlab.org. So, that’s S, T, E, B, E, R, L, A, B, .org. The “B” in Steber is B as in boy. You can probably also find it by searching for “P&W falling numbers.”

Drew Lyon: Okay. And I think we have a connection on our Wheat and Small grains website that will take people to your, to that particular website where all that data is located. So, that’s an excellent source. So, a defect. How did this defect come about? Has it always been there? Have we just discovered it or is it something that came in with some germplasm that we don’t know about and now is been crossed into lots of things? We have to go find it and get it out of there. What’s the story there?

Camille Steber: Well, the LMA was first described by an Australian named Daryl Mares in Australian germplasm and we pretty much – it hasn’t been on our radar until recently. Daryl thought that it came from cimmyt germplasm, that when people were doing crossing to wild relatives of wheat to bring in new sources of disease resistance, that they were accidentally moving in these genes that were causing late maturity alpha amylase or LMA. So, that’s Daryl’s theory.

Drew Lyon: And cimmyt for some of those people may not know, is an international wheat breeding program in Mexico, is it?

Camille Steber:  Yes.

Drew Lyon: Yeah. So, okay.

Camille Steber: So, yeah. That’s Daryl’s theory. I’ve seen LMA in varieties like Eltan which really doesn’t have any cimmyt germplasm in it, but I can’t, I can’t dispute. It still could’ve come from wide crosses to bring in disease resistance.

Drew Lyon: Okay. So, it’s been around and it’s just kind of come onto our radar screen so now we’re looking for it. One of those things if you look for something, you’re bound to find it kind of thing.

Camille Steber: In terms of testing wheat for LMA susceptibility, it is in my opinion one of the biggest pain in the necks that I’ve ever worked with [both chuckle]. The wheat is only susceptible during a very specific window of development and we have to be out there in the field and find wheat at the right stage, get it into a cold chamber and then all of that has to be ground up and put through alpha-amylase enzyme assays. 2017, we ran testing on something like 1,200 lines, last summer on 1,300 lines. It basically takes us the whole following year until the start of the next field season to get all the testing done, but that’s really been our major effort. We’re really playing catch up here. We need to get rid of the LMA susceptibility in our winter wheat.

Drew Lyon: Okay. So, how are you and your collaborators planning on going about doing that?

Camille Steber:  Well, we’re, we’re screening wheat germplasm from the breeding programs because we want the wheat breeders to be able to find the more resistant lines and stuff that’s ready to be released. So, I’m hoping that farmers will be seeing more and more resistant varieties as new releases come out and we’re mapping those genes. We need to have molecular markers so that Camille can do fewer LMA tests in the field next year [chuckles].

Drew Lyon: Okay. And how is that coming? Are you finding markers that are useful or is that?

Camille Steber: We’ve got data. Can’t tell you yet.

Drew Lyon: Okay.

Both: Stay tuned.

Drew Lyon: There you go. So, as you and your collaborators work on that, what are some things farmers can do to help reduce their risk of low falling numbers?

Camille Steber: Well, they can make use of the website that I mentioned and I, there are, there’s a lot of variation in falling numbers but there are certain varieties that are always at the bottom or often at the bottom of the pile for low falling number. They need to steer clear of those varieties like Bruehl, Xerpha, Jasper’s a new one. Maybe I’ll stop there, but you take a look at the website and look for the ones that are at the top. LCS Hulk actually did pretty well this year.

Drew Lyon: Okay. So, we’ll make sure we get the, in our show notes, that link so people can go to it because it is a wealth of information. It’s the best thing out there that we have right now and hopefully, that information will move into some of the guides that come, the growers so they can see that overtime. So.

Camille Steber: Yeah and right now we’re working on statistical analysis of that variety trial data, trying to come up with a good objective way of saying here’s the probability that any particular variety is likely to say be over 300 seconds so that you know, you can quantitate. I’ve had a lot of farmers complain to me that, you know, we now have data going all the way back to 2013 and it’s a pain to look at it all. They want some way to summarize it.

Drew Lyon: And as you said before, there’s quite a bit of variability, different varieties at different sites may behave. So, it’s hard to except for a few of the really bad ones or the really good ones, it’s hard to really make fine separations and that’s-

Camille Steber:  That is absolutely true. I mean, the other thing that drives me crazy about LMA is that it’s, it’s so variable that, you know, you wind up being able to see the extremes best. The ones in the middle are tough.

Drew Lyon: Yeah and I think one of the frustrations of the growers is in spite of all this variability, that 300 number is just rock solid. You know, buyers don’t seem to want to buy anything that falls a little bit below that and so despite the fact that there’s all this variability, it’s a set deal and they have to live with it.

Camille Steber:  Yeah and you know, the falling numbers test was invented back in the 1960’s. It wasn’t intended to be such a, you know, line in the sand. It’s being used in a way that’s not the way it was originally intended. It’s not a surgical kind of a number.

Drew Lyon: Right. So. And I believe there’s some people trying to find different approaches but so far nothing has proven all that successful or is that true?

Camille Steber:  Well, we’re interested in developing an ELISA assay for low falling numbers. We have a collaborative project going on right now with a biochemist at WSU and Andy McCubbin and wheat breeder Michael Pumphrey. An ELISA assay is a lot like a pregnancy test, it uses the same sort of technology where we should be able to estimate the falling number based on detection of the alpha-amylase protein in the meal. Similar sorts of assays are used right now to detect vomitoxin so that you know if you have, if you have damage from fusarium head blight. So, if we develop a tool like that, I can’t say that our foreign customers will accept that as a replacement for falling number, but it certainly provides us with a tool at the elevator to sort the good from the bad so that we don’t mix our low falling number wheat with our high falling number wheat. Because alpha-amylase is an enzyme, it’s a catalyst which means it take very few bad apples to spoil the lot.

Drew Lyon: Okay.

Camille Steber:  So, we need to protect the value of our wheat.

Drew Lyon: Well, it sounds like there’s some interesting things happening on the low falling numbers battlefield [Camille chuckles] and our listeners need to check out your website, steberlabs.org?

Camille Steber: Steberlab.

Both: Lab, singular, .org

Drew Lyon: And just keep up with this because there’s a lot of effort going into it right now. So, hopefully, some good, good, changes coming I guess. Well, thank you very much Camille. I appreciate your time.

Camille Steber: My pleasure. Thank you for inviting me.

[ Music ]

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat Podcast. If you like what you hear, you can subscribe on iTunes or your favorite podcasting app so you never miss an episode. And leave us a review while you’re there. If you have questions for us that you’d like to hear addressed on future episodes, please email me at drew.lyon@wsu.edu. You can find us online at smallgrains.wsu.edu. You can also reach out on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat Podcast is a production of CAHNRS communications in the College of Agricultural, Human, and Natural Resource Sciences at Washington State University. I’m Drew Lyon. We’ll see you next week.

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