What’s Interesting About Late-Maturity Alpha Amylase with Elliott Marston

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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.


My guest today is Elliott Marston. Elliott is a WSU plant pathology Ph.D. candidate studying under Dr. Deven See with the USDA-ARS Wheat Health, Genetics, and Quality Research Unit in Pullman, Washington. Elliott became interested in plant pathology while working for Dr. Xianming Chen’s stripe rust research project while completing his B.S. in agricultural biotechnology at WSU. His research in graduate school has focused on identifying potential genes associated with low falling numbers and late-maturity alpha amylase, specifically in PNW wheat.

Elliott is heavily involved in the Plant Pathology Graduate Student Association as an officer and has assisted with teaching as well as Extension and outreach activities within his department. Hello, Elliott.

Elliott Marston: Hi, Drew.

Drew Lyon: Good to have you here today to be my guest. I wonder if you can talk a little bit about what LMA is–that is late-maturity alpha amylase–and what differentiates it from other sources of low falling numbers such as pre-harvest sprouting.

Elliott Marston: Sure, I’d be happy to talk about that. So, what low falling numbers issues have in common is that at the end of the day, all of these wheat lines have retained high levels of alpha amylase post-harvest. And there a couple of different ways where we get to that high level of post-harvest alpha amylase.

In the instance of pre-harvest sprouting, what’s happened is prior to the wheat being harvested, due to usually either poor dormancy or adverse weather conditions, the grain has actually sprouted in the field before being harvested and that process of sprouting activates these enzymes and other proteolytic enzymes within the wheat and causes these elevated levels of alpha amylase.

Now, that’s not the only way that we get these high levels of alpha amylase. We also have late-maturity alpha amylase, which again we see that retained high levels of alpha amylase post-harvest, but the cause isn’t sprouting. Late-maturity alpha amylase specifically is high levels of alpha amylase post-harvest in the absence of sprouting.

Traditionally, when we first learned about late-maturity alpha amylase, we thought that this only happened when the wheat was exposed to a cold shock during the late- to mid- grain fill stages. But now that we know a little bit more about it, that’s not necessarily true. These high levels of alpha amylase can happen constitutively throughout the entire grain maturation process of the wheat in the absence of a cold shock or if the plant is grown during extended cold conditions, we could also see that as well.

Drew Lyon: Okay. That’s interesting, because my understanding was it was due to this big change in temperature, usually a cold snap somewhere at a critical time. But you’re telling me it can happen anytime?

Elliott Marston: Yes.

Drew Lyon: Okay. That’s interesting. So, how do you deal with that?

Elliott Marston: Well, it’s really interesting. And what you mentioned is true. When we first discovered late-maturity alpha amylase, we thought that this only happened in response to a cold shock. Now that we understand a little bit more about late-maturity alpha amylase, we understand that the reason that we see this happen with the presence of a cold shock is when temperature is lower, plants become a lot more responsive to a specific plant hormone called gibberellic acid or GA.

And so, these hormones are present in the plant the whole time that it’s growing–you’ll see levels go up and down depending on the different growth stage or life stage that plant is in–and so, those hormones are present the whole time. But specifically in the wheat that we grow here in the Pacific Northwest, that are semi-dwarf or double-dwarf wheat, they are to a certain degree insensitive to that GA hormone. The hormone is present, but the plant can’t sense it and can’t respond to the signal that’s happening there. When the temperature is lower, the plant all of a sudden is more responsive and sensitive to that hormone, so all of a sudden the signals that the hormone is sending can get through to the plant in those cold temperatures.

Drew Lyon: Interesting. And so, is that kind of what your research in LMA is about? Or, can you tell us a little bit about what specifically you’re doing in your Ph.D. program?

Elliott Marston: Yes. So, my project specifically, we’re searching for genes and regions of the genome that are associated with these high levels of alpha amylase. In theory, we’re hoping to identify specific genes that are responsible for differences that we see in the levels of amylase that are produced. Right now, it seems that to a certain degree, no matter the level of GA insensitivity, a lot of wheat is going to produce at least a little bit of alpha amylase in response to a cold shock, but there is variation in the amount of amylase produced. So, we’re trying to identify variations in the genetics for those lower levels of amylase in response to cold shock.

Drew Lyon: Okay. What would you do with that once you know that, what happens—is it that breeders are able to try to breed that out?

Elliott Marston: Exactly. So, once we identify the genes and the regions of the genomes that are associated with those elevated levels of alpha amylase, we can develop markers and then the genetic markers that we develop, Mike Pumphrey, Arron Carter, Kim [Garland-]Campbell can use that information to make breeding decisions in their programs and hopefully release some really strong wheat lines for PNW breeders that will be more resistant to low falling number issues.

Drew Lyon: Okay. I think I know that it’s kind of a tradeoff, right? If you breed a variety that’s going to be less susceptible to that pre-harvest, you also might have a variety that when you plant it in the field, doesn’t germinate when you want it to. So?

Elliott Marston: Right. That’s true for pre-harvest sprouting. What we’re seeing with LMA is that LMA susceptibility or resistance doesn’t appear to be linked to dormancy. So, in theory, hopefully we can identify some genes where we can control the overall level of amylase that’s produced without directly impacting germination issues like you’re talking about or general plant growth. But you’re right, we don’t want to totally turn off the sensitivity to the GA hormone because that would impact things like general plant growth and germination as well. So, it’s a fine line to walk in figuring out what we can turn off or turn down in terms of genetics without negatively impacting the overall plant performance.

Drew Lyon: Okay. Very interesting. I’m learning a lot here that I didn’t know just a few minutes ago. So, what’s something about LMA that you wish more people knew?

Elliott Marston: Well, I guess this kind of goes back to something we’ve already talked about, but something that I wish more people knew, is that LMA is not a genetic defect. And that was something that was a phrase that was used a lot in the early years of LMA when we were first discovering this issue is that LMA is a genetic defect. This is an issue, a mutation that we’re seeing in wheat that’s causing this.

And now that more research has come out, we’re realizing that wild wheat, landraces of wheat, ancient wheat progenitors, all naturally have it appear. It appears that these landraces of wheat that don’t have dwarfing genes and are not GA insensitive, naturally produce elevated levels of alpha amylase throughout their grain maturation period.

From the plant’s perspective, it makes sense to have elevated levels of alpha amylase in your seeds when you’re going through grain maturation. If that alpha amylase is present in the seed, then the next season when you’re germinating, you’re going to get a head start on your germination process. And it’s an evolutionary advantage from the plant’s perspective to have that in its back pocket with elevated alpha amylase levels.

We just haven’t seen that happening in our wheat production here in Washington because we’ve been using the semi-dwarf and double-dwarf varieties for the majority across the state for the last 50 years, essentially. So, with that inherent GA insensitivity, it felt like an issue suddenly appeared when really the conditions have just changed to cause this issue to happen more regularly.

Drew Lyon: Okay. So, will our problems with LMA be solved once we have a test to differentiate between LMA and pre-harvest sprouting? And can we easily identify LMA susceptible material?

Elliott Marston: That’s a great question. Amber Hauvermale and Camille Steber are doing a lot of great work specifically to help develop a test to maybe not replace a blind number test, but to supplement it because the existing falling numbers test can’t differentiate currently between different sources of low falling numbers–all it says is you’ve got low falling numbers or you don’t.

And this is obviously an issue because more and more research is coming out that LMA-affected grain doesn’t necessarily have the same quality impacts as pre-harvest sprouting affected grain. So, from the growers’ perspective, many of them feel like they’re being unfairly penalized for having wheat that obviously is failing the low falling numbers test but isn’t inherently lower quality like sprouted grain is. So, they’d really like a test to differentiate between the material so they don’t get that discount from the failing low falling number test that we see with sprouted grain.

The problem is, right now, even if we had that test that was cheap, fast, and accurate [and] could be done at the at the grain elevators to differentiate between the two issues, there currently isn’t a market for that LMA wheat. And so, until there’s a market for that specific subset of wheat, the market itself isn’t currently motivated to make that differentiation between LMA- affected grain and pre-harvest sprouted grain.

Once we have a market and the test in place, then growers will no longer be impacted by that discount. For now, until the market responds appropriately to this issue, from our side, all we can really do is breed lines that are more resistant or more tolerant to LMA susceptibility issues and also give as much good information to growers as we can so they can make educated decisions about the risk factors.

Drew Lyon: It sounds like you’re doing some real good fundamental research to get a better feel for it—because, like I say, even today I’ve learned some things I didn’t know and I think do have real repercussions for how we deal with LMA and sprouting wheat. So, thank you for sharing your information. When do you finish up your program?

Elliott Marston: Hopefully I’ll be finishing up here in the spring or summer. It’s a bit iffy about how long it’ll take me to finish up all of my data analysis and writing.

Drew Lyon: Okay. Well, is there a place somebody can go to see this research someday when it comes out?

Elliott Marston: Okay, so you can go ahead and check out our WSU plant pathology website,  find the Western Regional Small Grains Genotyping Lab website under Dr. Devin See, that’s there on our faculty page, and you’ll find an overview of all of the work that my lab is currently working on, including our work on late-maturity alpha amylase.

Drew Lyon: Okay, we’ll make sure we get that link into our show notes so people can go find it if they’re interested. Thank you very much, Elliott. Very interesting. I enjoyed talking with you today.

Elliott Marston: Thank you, Drew.

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 [X] @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.