Herbicide Resistance & Jointed Goatgrass with Jeanette Rodriguez

Jointed goatgrass.

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Show Notes & Resources Mentioned:

Contact Information:

Jeanette has graduated. For questions or comments, contact Ian Burke via email icburke@wsu.edu or by phone at 509-335-2858.

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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 ]

My guest today is Jeanette Rodriguez. Jeanette is from Central Washington. She did her undergraduate studies at Heritage University and graduated with a BS in Biomedical Science. As an undergrad, she did two summers of research at WSU in Dr. Amit Dhingra’s Research Experience for Undergrads Program and was placed in the Weed Science lab with Dr. Ian Burke. She enjoyed her time in this program so much that in the summer of 2016, she joined his lab as a master student. She is now in the process of finishing up her degree and defending her thesis on Herbicide Resistance and Jointed Goatgrass. Hello Jeanette.

Jeanette Rodriguez: Hi Drew.

Drew Lyon: So exciting time trying to finish up that master’s degree. And on a very interesting project, so I’d like to visit with you a little bit about that. So jointed goatgrass, where was this resistant jointed goatgrass sample found and in what crop?

Jeanette Rodriguez: So it was found in 2015 and it was found in Eastern Washington, so close by to Pullman. It was on a continuous rotation of Clearfield winter wheat and the grower brought it in a sample and we decided to go on this project and see where it led.

Drew Lyon: Okay, so kind of the situation as a weed scientist I’ve been saying we shouldn’t do…

Jeanette Rodriguez: Exactly.

Drew Lyon: developed what we feared but I guess it did take longer than I — when this technology came out in about 2000 I thought, it was about a ten-year technology and it’s almost lasted twice that long. And this is I think the first case of resistant jointed goatgrass in the country, isn’t it?

Jeanette Rodriguez: Yeah, to our knowledge this is the first sample that we received in the Weed Science Lab with Dr. Ian Burke. We’re hoping that maybe this will broadcast this more and other growers will take an interest and if they see anything developing they can send it into our program and we can screen it.

Drew Lyon: All right, great. So what does the jointed goatgrass sample resistant to?

Jeanette Rodriguez: So the sample was sent in with the suspicion of imazamox resistance.

Drew Lyon: Imazamox is the active ingredient Beyond herbicide, so the Clearfield wheat system.

Jeanette Rodriguez: Exactly. So we went ahead and tested it to the imazamox and then we also tested it to mesosulfuron because mesosulfuron is also used to control, suppress, not really control it, so we threw that in there to test it so our sample came back positive for imazamox and mesosulfuron resistance.

Drew Lyon: Okay, and mesosulfuron is the active ingredient in Osprey.

Jeanette Rodriguez: Correct.

Drew Lyon: Okay. So resistant to both. It was sent in because they thought it was imazamox but through testing, you found it was resistant to both imazamox and mesosulfuron.

Jeanette Rodriguez: Exactly.

Drew Lyon: Interesting. Okay, what is the level of resistance? Is it one time or two times more resistant, four times?

Jeanette Rodriguez: So for the imazamox, it was 14 times more resistant than our tested susceptible, which is very high what we were seeing based on what an application rate would be in a typical field. The mesosulfuron was five times more resistant than our susceptible so again five times is just incredible how much it was resistant.

Drew Lyon: Okay, so it would be — basically it would become uneconomical to try to control it with either one of those products.

Jeanette Rodriguez: Exactly.

Drew Lyon: Why is imazamox resistant jointed goatgrass such a concern?

Jeanette Rodriguez: So the resistant jointed goatgrass poses a threat to the new technology of the Clearfield winter wheat because we have limited herbicide options for controlling it.

Drew Lyon: Yeah, I remember back in Nebraska, before Clearfield Wheat it was not an easy weed to deal with and then Clearfield Wheat came along and all of a sudden we had a very effective tool and now we’re in jeopardy of losing that, which would be a big hit I think.

Jeanette Rodriguez: Yeah, it becomes difficult to treat annual weeds and annual crops.

Drew Lyon: Yeah and goatgrass is genetically related to winter wheat so it makes it even more difficult. So as I mentioned earlier I would have expected that we would have seen this resistance pop up maybe five, ten years ago, we haven’t, why is it taking so long do you think for this resistance to show up?

Jeanette Rodriguez: I think growers have been using the technology with Clearfield and using crop rotation and not just depending on this technology to suppress the goatgrass with mesosulfuron and imazamox. So I think that now maybe the way that it was used wasn’t the proper stewardship by just using a continuous Clearfield rotation, maybe throwing in a fallow, and the mutation could have developed over time.

Drew Lyon: Okay. It definitely has lasted longer than many thought and you know, as far as I know this is the only case so if the grower can do a good job of eradicating this maybe it won’t spread and it will be a while yet before it becomes a widespread problem.

Jeanette Rodriguez: Exactly.

Drew Lyon: What are some of the preventative strategies people can use to control jointed goatgrass?

Jeanette Rodriguez: I think controlling in a fallow, so maybe spraying out with glyphosate if you do see dense patches. Doing some crop rotation into the pulses, that’s another way you can take advantage of the ACCase inhibitors, throw those in and help eradicate your jointed goatgrass population.

Drew Lyon: So was this case, I know there was some work done in Oregon by Dr. Carol Mallory-Smith about the potential risk of hybridization of the pollen from imazamox resistant wheat crossing over to goatgrass, which is related and then that’s the way it was delivered. Do you think that’s how this occurred or was it some other method?

Jeanette Rodriguez: That was an initial concern because we really didn’t know much about it when we first started working with it. Prior to me coming in and taking over this project, someone actually used the BASF genotyping protocol that they have, went through the whole procedure and then were able to rule out that it wasn’t a case of that particular mutation that’s in the Clearfield variety. It wasn’t what we found in our resistant jointed goatgrass population.

Drew Lyon: Okay. so it was developed through just a natural —

Both: Natural mutation process.

Drew Lyon: — out in the field and by repeated selection pressure on the population. Okay, what type of resistance are you seeing in the resistant jointed goatgrass?

Jeanette Rodriguez: So what we’re seeing is a target based resistance with an amino acid substitution in the ALS gene that is causing the high levels of imazamox resistance and what we’re seeing with the mesosulfuron the SU’s and the ALS’s.

Drew Lyon: Okay, so just a single amino acid substitution and changes the shape of the —

Jeanette Rodriguez: Of the little protein and binding sites and you don’t get effective control with your imazamox.

Drew Lyon: Okay, so it’s not like what we’re seeing or what people are seeing with like Kochia, where the Kochia is just producing more and more metabolize — or more and more ESPS synthase so you just can’t get enough glyphosate into the plant.

Jeanette Rodriguez: Yeah, no.

Drew Lyon: This is actually more —

Jeanette Rodriguez: A plant mutation, yeah. But we’re thinking based on the genetic testing that I’ve been doing in the lab and what we were seeing. We also created a bi-parental population so we actually crossed a resistant and a susceptible jointed goatgrass so we were able to track the mutation as it was being brought down to the F2 population.

Drew Lyon: Okay. And what did you see there?

Jeanette Rodriguez: We were also able to see that — so we started with the alanine 122 mutation, which is what we saw that was causing the resistant in our original jointed goatgrass. We crossed it with a susceptible biotype and as we crossed it in our second generation we were able to see that the population segregated so some of it was resistant, some of it was susceptible, and then some of it had an intermediate kind of category and we were able to track that point mutation down to the progeny.

Drew Lyon: Okay, so you have a pretty good idea how this resistance works and that’s pretty important information too when it comes to how we go about managing. So you mentioned earlier the ACCase inhibitor working Assure II is a product that we use quite a bit in pulse production. Will that be effect of Select, Assure II, those kinds of products are still effective on this or there’s some cross resistance there?

Jeanette Rodriguez: We did another screening where we used the ACCase inhibitors and ALS inhibitors and clethodim and quizalofop both controlled the jointed goatgrass population so we’re not seeing cross-resistance within the different herbicide modes of actions.

Drew Lyon: Okay, that’s good. So some resistance within the group II, any other group II’s showing resistance other than imazosulfuron and imazamox?

Jeanette Rodriguez: We saw imazapic, mesosulfuron, and trifloxysulfuron that also flagged in our screening of the resistant population. So those didn’t quite control the resistant population.

Drew Lyon: Okay, okay. Interesting. So we’ve seen the Group II’s, which we’ve had now for almost 20 years. We’re seeing more and more resistance issues and it sounds like goatgrass which, like I said back in the ’90s was a major problem, Clearfield wheat came along, really gave our growers a solution and hopefully we’re not about to lose that.

Jeanette Rodriguez: [chuckles] Hopefully not.

Drew Lyon: And even the mesosulfuron the fact that’s it’s resistant, the mesosulfuron is somewhat troublesome because that’s what most growers use in the non-Clearfield to stay on top of it.

Jeanette Rodriguez: Exactly. And it’s not only the goatgrass that we’re seeing, we’re receiving other samples. We test downy brome, Italian ryegrass and we’re also seeing some beyond resistance in that brome samples that we’ve been getting. So reliance on the Group II’s is causing trouble with trying to control all these different weeds.

Drew Lyon: So you haven’t published your thesis yet but if somebody wants to go learn a little bit more about this is there any information, any place they can go to learn about it or do we wait for your thesis to come out and then we all check it out of the library?

Jeanette Rodriguez: Some of my work was actually presented at the conference at the WSWS.

Drew Lyon: Okay, at the Western Society of Weed Science, OK.

Jeanette Rodriguez: Yes. So I have an abstract. I presented a poster and I gave a talk.

Drew Lyon: Okay.

Jeanette Rodriguez: So there’s some information there and yeah, we’ll just have to wait for my thesis.

Drew Lyon: Okay. And what do you plan on doing after your degree?

Jeanette Rodriguez: Hopefully land a job somewhere. [Drew chuckles] I’m looking at moving Iowa.

Drew Lyon: Okay.

Jeanette Rodriguez: So hopefully some prospects down there and learn some different cropping systems down there and exciting future.

Drew Lyon: Okay, well we wish you the best of luck. Thank you very much for your time.

Jeanette Rodriguez: 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.