Hooked on Falling Numbers with Dr. Camille Steber

March 21, 2022

Show Notes & Resources Mentioned:

Contact Information:

Contact Camille Steber via email at camille.steber@usda.gov.

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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 podcast app and leave us a review so others can find the show too.

[ Music ]

Drew Lyon: My guest today is Dr. Camille Steber. Camille is a research geneticist with the USDA-ARS Wheat Health, Genetics and Quality Unit. She has an adjunct faculty appointment in the WSU Department of Crop and Soil Sciences in Pullman. Camille obtained her Ph.D. from the University of Chicago in Molecular Genetics. She did her postdoctoral work on how hormones control seed germination at the University of Toronto. She has been with the USDA-ARS for 24 years, working on seed germination, pre-harvest sprouting, and the falling numbers problem in wheat. Hello, Camille.

Dr. Camille Steber: Hi, Drew. Yeah. I can’t believe it’s 24 years. [ Laughter ]

Drew Lyon: They do add up quickly at some point, don’t they? Well, so I think we’ve talked about falling numbers in the past, but for those who might be new to the idea, can you give us a little explanation of what the falling numbers test is?

Dr. Camille Steber: Yeah. So this Hagberg-Perton’s falling numbers method was developed in the 1960s as a way to detect alpha amylase enzyme from pre-harvest sprouting in wheat grain. Pre-harvest sprouting is when the wheat grain starts to germinate on the mother plant when we have rain before harvest, you know, an untimely rain event. And the production of alpha amylase during germination is really a natural part of germination; that enzyme digests the starch into sugars that then the growing wheat seedling can use to fuel its growth until it clears the soil and has access to the sun and can fuel itself off of photosynthesis. So alpha amylase is found in human saliva. It’s a very common enzyme, but while it’s good for digesting food, it’s not good for end-use quality when we turn our grain into flour. It tends to result in cakes that fall, a sticky bread that gums up slicing machines, and in mushy noodles. So the falling numbers test itself can protect millers and bakers from risk of financial loss due to poor end-use quality. But farmers still receive serious discounts when they have falling numbers below 300 seconds. Only way that we can help reduce their risk, I think, is through good genetics.

Drew Lyon: Okay, so tell us how you became interested in falling numbers. You’ve obviously studied other things in your past. What got you hooked on falling numbers?

Dr. Camille Steber: So I first learned about the falling numbers problem in 2011 when Arron Carter and Michael Pumphrey, the WSU breeders, approached me and asked me to collaborate with them on this project and I really jumped at the chance to work with them on this because I’d spent a lot of my career working on seed germination and wheat pre-harvest sprouting. And, you know, one of the best things that can happen to a scientist is to be asked to work on a real life problem that’s right up your alley. [ Drew chuckles ] So I jumped on it and didn’t look back. That project then — we were working on breeding for resistance to a low falling numbers and that project received a great deal of attention in 2016 when we had our problem — a big problem with low falling numbers. And the project continues till this day.

Drew Lyon: Okay. So still, still trying to solve that issue. What have you learned so far?

Dr. Camille Steber: So one of the first things we learned in that project that we weren’t just having problems with low falling numbers due to sprout induced rain. We were sometimes having problems with low falling numbers when there had been no drought inducing rain at all. This turned out to be a problem, a weather problem called late maturity alpha amylase or LMA.

Drew Lyon: Okay, so what is LMA?

Dr. Camille Steber: It’s production of alpha amylase during the soft dose stage of grain filling when the wheat experiences a cold shock or cool temperatures during that stage of development. It actually has turned out to be a serious problem, especially in the winter wheat, so it means that farmers who don’t have a problem with sprout inducing rain may still have problems with low falling numbers. So when we first started the project, we had no idea that LMA was a problem for wheat. And we’ve really progressed a lot since then. We’ve developed a good testing system. It’s slow and laborious but we’ve been able to look at elite breeding lines and at mapping populations with the aim being to map genes for susceptibility to LMA so that we can select against this and early breeding material. You know, early generations or we need to look at something like 5,000 lines a year if we want to root this out early in the program before the breeder has invested a great deal. Before having to throw things out just because they have LMA. So we’re at the point now where we have mapped genes for LMA in Pacific Northwest wheat. We still have a ways to go. We’re collaborating with Deven See of the USDA genotyping lab to take these markers we’ve found in mapping populations and make certain that those markers work for us in the variety trials and in our breeding programs. It’s really important to get to this state. When you hear me use the word “mapping”, I’m not — we don’t right from the beginning know exactly where the gene is. So like if I were the gene for late maturity, alpha amylase, you know, initially when we map, someone might say, well, she’s in North America, but then we’d have to move in a little closer and say, well, she’s in Washington or she’s in Pullman, And finally, you get to the point where you say, well, her office is on the second floor of Johnson Hall, and then you’re finally at a point where you can select with confidence in a breeding program.

Drew Lyon: So where would you say you’re at at this stage? [ both laugh ]

Dr. Camille Steber: We’re on the long arm of chromosome seven B. We have a lot of things like that where we’re in the general area and we have a marker that’s like a street sign that we can say is kind of close to that gene. But we have to make certain that that street sign works in all of our germplasm before we can be confident that we can use that to select for resistance in our breeding programs.

Drew Lyon: Okay, you’re on your way, but you’re not there yet.

Dr. Camille Steber: We’re on our way.

Drew Lyon: Okay. So you mentioned the LMA is caused by cool temperatures. So in a year like 2021, where cool as hard to find at least during the growing season. [ Camille laughs ] Does that mean LMA wasn’t a problem in 2021?

Dr. Camille Steber: You’re really right about that Drew. We’ve been performing falling numbers, testing of the Cereal Variety Trials since 2013 and 2021 was one of the best years for high falling number that we’ve seen.

Drew Lyon: Okay. So global climate change is going to be good for this problem?

Dr. Camille Steber: Yes and no. [ Drew laughs ] Actually, there was just a paper recently out of Australia where they claim no, it’s going to be very bad for falling numbers. This is because we have these two things going on: pre-harvest sprouting and LMA. Pre-harvest sprouting tolerance, you have less pre-harvest sprouting tolerance when the grain experiences high temperatures during grain filling. So it means that if you had extreme heat like last year followed by serious rainfall, you’d be in trouble.

Drew Lyon: Interesting.

Dr. Camille Steber: But it’s good for preventing LMA. It can cause problems with elevated alpha amylase though by getting in the way of seed maturation. We’ve seen, actually long ago I had this experience with a farmer named Brian Cochran where he sent me his grain that had low falling numbers, and we found that low falling numbers was associated with green seeds. So alpha amylase is actually present early in development and has to go away as the seed matures. If you have green seeds mixed in with your mature wheat, they’ll have elevated alpha amylase and cause a problem. If you have high heat, as the wheat is maturing, you wind up with this shriveled grain that hasn’t done well in grain filling. Sometimes those will be green and have elevated alpha amylase really because the seed didn’t mature well. So extreme heat can cause problems in many ways. That maybe a mild global warming, where we have warmer temperatures not scalding, will help. [ Drew laughs ]

Drew Lyon: Well, we’ll try to dial that in for ya. [ Camille laughs ]

Dr. Camille Steber: Work on the weather machine. [ Drew laughs ]

Drew Lyon: So what can farmers due to lower the risk of low falling numbers?

Dr. Camille Steber: So farmers can avoid varieties that are susceptible to low falling number. We have been posting falling numbers from the WSU Cereal Variety Trials on the web at steberlab.org since 2013 so we have many years worth of data. Kim Garland-Campbell has done a statistical analysis of this data to identify varieties with more or less stable falling numbers and she has contributed that information to the Small Grains website where they have the Variety Selection Tool.

Drew Lyon: Okay.

Dr. Camille Steber: So you can incorporate that into your variety selection. High Line Grain also has analyzed that data and made that part of their recommendations for varieties. There are other things that can help. Some of what you’ve heard me say before. Avoid harvesting immature grain if you can possibly help it. When your wheat is mature harvest pretty quickly to reduce the length of time during which you might have a sprout inducing rain. Avoid mixing high falling number wheat with low falling numbers wheat. It’s true that the fellows at the elevator do some of that blending, but it really takes very little low falling numbers grain to spoil a lot of high falling numbers wheat and it’s best to leave that blending to the professionals. So if you find that you need to grow a susceptible cultivar like Bruehl because it has a good emergence or a good disease resistance package, consider maybe planting on both a high risk and low risk falling number variety at the same time and then harvest those two things separately. Maybe your riskier variety will yield better, but you still have some wheat that’s a backup that’s more likely to have a high falling number and have less trouble with discounts.

Drew Lyon: Those are all sound pieces of advice. I know I was in western Nebraska for a long time and harvest quick was was the rule of thumb because of hail. And here it might be low falling numbers to avoid pre-harvest sprout. [ Drew chuckles ]

Dr. Camille Steber: Yeah. Harvest quick to avoid rain. [ both laugh ]

Drew Lyon: Which is rare but it does happen, doesn’t it? Thank you very much, Camille. We appreciate you spending some time to explain low falling numbers and what your group is doing to try to address that.

Dr. Camille Steber: Thank you for having me, 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 podcast app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon — that’s lyon@wsu.edu — (drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu 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.

The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.