Pre-harvest Sprouting and Falling Numbers in Wheat with Stephanie Sjoberg

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Contact Stephanie Sjoberg via email at stephanie.sjoberg@wsu.edu


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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 Stephanie Sjoberg. Stephanie is a third-year doctoral candidate, jointly advised by Drs. Arron Carter and Camille Steber. She is studying preharvest sprouting and falling numbers in wheat. She is born and raised in Washington and came back to the state to pursue her Ph.D. in Crop Science after working at a vegetable seed company in California for several years. Hello, Stephanie.

Stephanie Sjoberg: Hi, Drew.

Drew Lyon: So, Stephanie, falling numbers, would you remind our listeners about what causes low falling numbers in wheat?

Stephanie Sjoberg: Sure. So, for those who may not know, falling numbers is a test of starch degradation in wheat flour. It is used in order to determine if the flour is low quality. So if we have low starch, then we also see a loss of structural integrity in the cakes. This can be caused by two separate factors. We kind of consider them genetically apples to oranges. And they’re both triggered by environmental conditions. So one is preharvest sprouting. Preharvest sprouting is just in general the germination of a seed on the mother plant. That occurs during harvest when there’s rain. That’s visibly, you’re able to see that on the plant. But then our second factor is late maturity alpha-amylase and that is something that occurs during grain development. And if we see a spike in temperature, either high or low during that period of time, we see degradation in the seed. And that can only be detected by falling number test.

Drew Lyon: Okay. So two causes of it, both could be there, only one could be there, but if you have one or both, you have problems, or could have problems.

Stephanie Sjoberg: Right. Right.

Drew Lyon: Okay. So your work in the Steber lab is with some of the, I guess explain what you’re doing in the Steber lab. I know that we’ve had, 2016, I think, was a really bad falling numbers year. We had a lot of problems in the state. There’s a fair bit of data out there on how different varieties behave in these situations, but a lot of variability in that data as well. Can you talk to us a little bit about that?

Stephanie Sjoberg: Sure. So we have been running falling numbers on all of the cereal variety trials since 2011. And that was after about a thirteen-year hiatus when, from 1998 to 2011, there wasn’t a pressure for breeding for preharvest sprouting tolerance and LMA. So in 2011, we saw the environmental conditions that allowed for low falling numbers and that was when the Grain Commission decided to fund the Steber lab to run falling number on all the WSU cereal variety trials, so for spring wheat and winter wheat. In particular, 2013, ’14, and, as you mentioned, 2016, were quite bad years for falling number. And so what we’ve done is we’ve compiled all the data and we can look at it as a whole. When farmers look at it, it’s publicly available, when they look at it, it doesn’t look like there’s a trend in certain genotypes or varieties that are performing well in all locations. It’s hard to say from year to year. And not only that, but you can have locations that one year, for instance, Pullman can have low falling numbers in 2014 and then it had fine falling numbers in 2016. So it’s hard, there was some criticism of the data. So that would be why I decided to take on an analysis. And so I looked at every single location. We have 53 locations in three years. And we took weather data for each of those locations. And we were able to determine, based on the weather data, whether it could have been triggered by LMA which would be a heat or cold shock during that grain maturation time, or preharvest sprouting which was rain during, or near harvest, near harvest.

Drew Lyon: Okay.

Stephanie Sjoberg: So we are able to determine whether it was triggered by LMA or PHS. And then, of course, we have quite a few that weren’t affected at all so that would be no event. So we are able to factor that into our analysis. And then, using that, we are able to determine that the heritability is lower than maybe some other traits, but it’s around .25, which is pretty good. And it does give the breeders some inclination of how they’re supposed to breed for that. It also, we’re hoping it will allow us to develop models and look at the performance of varieties across years and locations and see which varieties are stable. So which varieties are stable in LMA environments and preharvest sprouting environments, and those are the ones that we can recommend to farmers at this time. So that would be, for instance, like Crescent, Puma, Otto, those are all good varieties that we feel comfortable telling farmers, recommending them to plant. Obviously, we would like to have additional varieties that are completely resistant to both. And so the goal of my Ph.D. is to identify preharvest sprouting tolerance in many varieties. We have a large panel of Pacific Northwest varieties that we’re using different experiments to identify the genes that are responsible for that. And then we can use that to improve our breeding lines.

Drew Lyon: Okay. Can we go back to something you said earlier? You talked about heritability. So for those of my listeners who aren’t plant breeders, could you tell us a little bit about what heritability is, what it means, and what a .25 might mean compared to some other .5, and some other trait?

Stephanie Sjoberg: Right. So heritability is on a scale of zero to 1. And heritability is made up of the genetics and also, well, so it’s — the phenotype that we see in the field is made up of genetics and environment factors. So environmental factors meaning, you know, for instance, the falling number situation. If we have low falling numbers, then it’s due to an environmental trigger. So that environmentally impacts the genetics. And that is actually an interaction. But when we’re talking about heritability, we’re talking about the genetics that are the part of the phenotype, the proportion of the phenotype, that is due directly to the genetics and not the environment. And so in yield we see a slightly, you know, anywhere between — not high. I don’t think it would be above .5. But those are still selectable traits. It means that it will require additional trialing and additional locations. But something like Mendel’s peas, the color or the wrinkled versus smooth, that is a Mendelian trait to that’s a heritability of 1.

Drew Lyon: Okay.

Stephanie Sjoberg: Right. So.

Drew Lyon: All right. So a .25 means there is potential to use genetics in breeding to improve it but it’s not going to be really easy.

Stephanie Sjoberg: One generation and done. Yeah.

Drew Lyon: You’re going to do a lot of testing and field testing to really zero in on that.

Stephanie Sjoberg: Mm-hmm.

Drew Lyon: Okay. Good. Thank you. So tell us a little bit about how you go about improving, or how you think you go about improving tolerance to preharvest sprouting in the breeding program.

Stephanie Sjoberg: Right. So we have a couple of different strategies. And so I mentioned that we’re doing some studies, so we’re doing a genome-wide association study looking at different traits related to preharvest sprouting. So we use an experiment in the greenhouse to test for sprouting. And we’re able to phenotype hundreds of lines in the greenhouse. We also run falling numbers which makes sense. That’s what the farmers use. And we also run alpha-amylase assays, so enzyme assays on our seeds.

Drew Lyon: Okay.

Stephanie Sjoberg: And so what I’m doing is using that phenotype information in combination with genome-wide markers which I’ve heard several people talk about on the podcast. And so we generally have markers that span across the entire genome and give us kind of a map of what different allele variation that we see across a large panel of genotypes. So I’m using a panel of 480 in addition to another panel of 320 lines. So we have quite a few. And we’re also looking at traits related to emergence because preharvest sprouting is 60 to 80% correlated with seed dormancy. And so we do not want to decrease the emergence, especially in the low rainfall zones, by improving preharvest sprouting. So that’s a really big concern. So that’s why we’re also using something called genomic selection which I believe Jeff talked about on the podcast.

Drew Lyon: Right.

Stephanie Sjoberg: And he talked about using it for different traits, but it also can be applied to other traits. And then we’re hoping that we can use that technique to improve preharvest sprouting and emergence or improve preharvest sprouting without affecting emergence.

Drew Lyon: Yeah. Because one way you could solve it is just breed dormancy into the seed.

Stephanie Sjoberg: Right.

Drew Lyon: And it wouldn’t happen but then you might have to wait three years before you could plant the seed.

Stephanie Sjoberg: Yeah. And I don’t think that would be an effective breeding tool.

Drew Lyon: It would be a very slow release time for new varieties.

Stephanie Sjoberg: Right.

Drew Lyon: So you mentioned this data on pre-harvest sprouting or low falling numbers is all available. Can you tell our listeners where they would go to find that information?

Stephanie Sjoberg: Yeah. So the Steber lab website, I believe there’s a link to it on the WSU cereal grains, or small grains, website. And it has everything. You can look at data by variety across all years, or you can look at it by location, or by year. It’s kind of up to you, pick your own adventure sort of thing.

Drew Lyon: Okay. Well, we’ll make sure we get that into our show notes so readers who are interested can go and find that information and play around with it. It’s a very important issue here in Washington. I know the Washington Grain Commission successfully got some money from the ARS to help us do this research and hopefully it’s something we all get figured out soon. But it sounds to me like it’s not going to be really fast or really easy. It’s going to require a lot of work from people like yourself. So keep at it and hopefully we’ll have some new information for our growers not too far down the road. Thank you very much, Stephanie.

Stephanie Sjoberg: Thank you, Drew.

[ 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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