Seed Treatment Decision-making
Don Lee
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05/23/2016
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For more information please visit the Oomycete Disease Diagnostics web page:
https://ge.unl.edu/oomycete-disease-diagnostics/
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- [00:00:06.107]Hello this is Don Lee
- [00:00:07.361]from the University of Nebraska at Lincoln
- [00:00:10.549]and I'm going to share the story
- [00:00:14.136]of work conducted by a network of
- [00:00:18.908]research and extension pathologists from
- [00:00:22.728]a number of universities in the United States
- [00:00:25.154]including those listed below and the focus of their work
- [00:00:28.452]is to get a better understanding of Oomycete disease
- [00:00:32.735]in soybean farmers fields and how seed treatments
- [00:00:35.603]might have an impact on this potential problem.
- [00:00:39.179]As we'll focus here on in this part of our lesson
- [00:00:43.537]and so most of what I'll share with you is work
- [00:00:46.695]conducted out of the laboratory of Doctor Martin Chilvers
- [00:00:50.213]at MSU who's leading this part of the network project
- [00:00:55.670]and the work that they're doing is to try to
- [00:01:01.800]be a benefit to soybean farmers who have certainly
- [00:01:04.818]the potential to grow a great soybean crop
- [00:01:07.663]but have problem areas in their fields if they encounter
- [00:01:13.383]maybe almost every year or maybe from year to year
- [00:01:17.317]depending on the situation and when this problem is
- [00:01:21.717]caused by soybean disease caused by Oomycete,
- [00:01:27.034]then seed treatment decision making
- [00:01:30.075]or maybe seed rate decision making is important.
- [00:01:33.431]And thinking about how they could avoid this problem
- [00:01:37.634]in the future, so maybe planting at a higher seedling.
- [00:01:40.873]A seed rate would make a difference.
- [00:01:44.251]A seed treatment might avoid this problem.
- [00:01:47.374]Maybe they did use a seed treatment
- [00:01:49.174]and they don't know why it failed.
- [00:01:52.540]Getting answers to these kinds of questions
- [00:01:55.374]is the goal of this work.
- [00:01:57.672]I'm going to include a couple of extension resources
- [00:02:01.132]in this learning environment that you can link to here
- [00:02:04.836]that will give you either a reminder, an update or
- [00:02:08.876]some background on seed treatments, here's one
- [00:02:12.278]supported by the United Soybean Board.
- [00:02:14.658]Here's one from Purdue University that's better looking
- [00:02:17.537]at fungicide efficacy on a variety of soybean diseases
- [00:02:21.276]so I encourage you to look at the information here
- [00:02:24.538]as a part of your learning in this environment.
- [00:02:27.638]So let's take a look at the work that
- [00:02:31.074]Doctor Chilvers group lead,
- [00:02:34.288]where their focus was to get answers to these questions.
- [00:02:37.578]What are the Oomycete communities
- [00:02:42.466]that are in farmers' fields?
- [00:02:44.521]What are the organisms that their soybean plants
- [00:02:47.351]are dealing with every year.
- [00:02:49.546]So to conduct this research, Doctor Chilvers
- [00:02:53.749]networked with his fellow extension pathologists
- [00:02:56.314]in a number of states, and asked them to go out
- [00:03:01.133]into soybean farmers fields that had seedling disease issues
- [00:03:06.207]and send samples in both 2011 and then samples from
- [00:03:11.524]some of the same, but also some different fields in 2012
- [00:03:15.808]so he could look at two years of samples collected
- [00:03:20.649]in the mayor soybean growing areas of the United States.
- [00:03:25.189]So, this is from an earlier presentation Doctor Chilvers
- [00:03:30.471]put together for our Oomycete learning environment.
- [00:03:33.571]So from these samples that would contain these disease,
- [00:03:37.925]soybean seedlings, you could use the methods
- [00:03:41.047]we learned about from the disease clinic
- [00:03:45.366]experts to culture isolates from these tissues
- [00:03:49.848]and then from these isolates they could either store those
- [00:03:53.563]or they could grow them in bulk to get biomass
- [00:03:56.508]for DNA extraction and then the DNA analysis
- [00:04:00.896]could be conducted and DNA sequence information
- [00:04:04.019]from each isolate determined and compared to identify the
- [00:04:08.728]species of Oomycete that was living on those plants, okay.
- [00:04:14.499]And so 3200 different cultures were analyzed this way
- [00:04:18.446]from the two years of samples collected
- [00:04:21.360]and based on the sequence analysis, 82 unique
- [00:04:25.621]Oomycete species could be identified.
- [00:04:28.767]Let's take a look at the results from the Chilvers lab then
- [00:04:32.239]and see how they came to the conclusion that Oomycetes
- [00:04:35.453]are a very diverse community living in these soil
- [00:04:40.108]ecosystems that
- [00:04:43.870]from farmers' fields.
- [00:04:45.936]So, here we can look at the frequency at which
- [00:04:49.139]a certain species occurred in an isolate, all right.
- [00:04:54.096]And some were very rare, and then some far more common.
- [00:04:58.566]Pythium sylveticum was the most
- [00:05:02.632]prevalent species identified in the isolates in 2011
- [00:05:06.672]so then they repeated this experiment in 2012.
- [00:05:10.352]They used growing conditions that were a little more
- [00:05:15.972]veered towards promoting growth of the Phytophthora species
- [00:05:19.423]which were not as commonly found as the Pythium
- [00:05:24.241]and what do you think of their results?
- [00:05:27.271]Are you surprised or not?
- [00:05:29.485]The results were, to my untrained eye,
- [00:05:32.446]indicating that, again there's a diversity,
- [00:05:36.021]again there are rare and more common,
- [00:05:39.423]but the most common species found in 2011
- [00:05:42.825]was also the most commonly occurring species in 2012
- [00:05:46.842]and so there is some variation from year to year
- [00:05:50.696]in the species, but overall, the same conclusion.
- [00:05:55.422]There's a diversity of Oomycete species
- [00:05:58.092]in these communities, some are more prevalent than others
- [00:06:01.854]and then this leads then to the next question.
- [00:06:05.174]So, the question is if we've got a diversity of
- [00:06:10.387]species that are living in these soil environments,
- [00:06:13.661]which ones are responsible for causing disease?
- [00:06:16.424]And are environmental conditions such as changes
- [00:06:20.569]in temperature important?
- [00:06:22.720]And which species are the most problematic for farmers?
- [00:06:27.933]So, what Doctor Chilvers team did then with this study
- [00:06:33.018]is they focused on understanding more about the
- [00:06:35.607]pathogenicity and then the virulence of specific species
- [00:06:43.595]grown from these isolates, so pathogenicity,
- [00:06:46.080]can it cause disease, virulence, to what degree
- [00:06:50.612]does disease progress, once it's initiated.
- [00:06:54.169]So I'm going to show results that Doctor Chilvers shared.
- [00:06:58.140]Seven different species from their study
- [00:07:03.143]and we're going to look at results from both
- [00:07:05.349]a seed rot and a seedling root rot assay.
- [00:07:08.958]All right, so here's the point where they can
- [00:07:13.303]collect data from their seed rot assay.
- [00:07:15.636]You can see here the Control and number of seeds
- [00:07:18.794]germinated in a petri dish environments
- [00:07:21.325]that's conducive for seed germination
- [00:07:25.458]and in this case, in the control no isolates were placed
- [00:07:29.515]in the presence of the seeds, with the other seven
- [00:07:34.982]a certain dose of the isolate was presented
- [00:07:39.324]and then you can get an idea of do they cause disease?
- [00:07:44.769]Is that isolate a pathogen?
- [00:07:48.008]And then, to what degree this disease progress?
- [00:07:52.860]And you can see that depending on the species
- [00:07:56.633]they saw various responses in terms of both a virulence
- [00:08:02.334]and pathogenicity that Pythium attrantheridium
- [00:08:09.265]in my untrained eye isn't much different than the Control.
- [00:08:13.212]You can also see that there is a difference between
- [00:08:15.150]the Pythiums, many of the Pythiums and Phytophthora
- [00:08:18.492]when it comes to seed rot.
- [00:08:20.547]Okay, so this kind of assay delivered more specific
- [00:08:23.670]information about what the individual species
- [00:08:28.987]of Oomycete living in those soil environments could do.
- [00:08:34.065]All right, so they conducted this seed rot assay
- [00:08:38.407]twice at two different temperatures.
- [00:08:41.031]At a cooler temperature and at a warmer temperature.
- [00:08:44.514]So let's take a look at the results here.
- [00:08:47.195]A lot of information in this table
- [00:08:48.937]so let's focus on a couple of specific species.
- [00:08:53.465]So here's a species in which it was much more
- [00:08:57.827]virulent, had a higher level of disease severity
- [00:09:01.078]at the cooler temp than at the warmer temp.
- [00:09:03.945]Other isolates don't show very much difference
- [00:09:08.241]between the two temperatures, and then some species
- [00:09:13.396]show the opposite effect, they show a virulence
- [00:09:16.670]at warmer temperatures, almost none at the cooler temps.
- [00:09:20.803]And then we have a collection of species like those here
- [00:09:24.553]that show a fairly high degree of disease severity
- [00:09:28.744]at both temperatures, so if you had these particular species
- [00:09:33.365]in your soybean field, it's likely to result in
- [00:09:38.880]disease issues, seed rot disease issues
- [00:09:42.142]in a variety of growing seasons,
- [00:09:46.747]early growing season conditions.
- [00:09:48.779]All right, so the other assay that they conducted
- [00:09:52.320]in the Chilvers lab was on seedlings,
- [00:09:56.244]and in particular looking at root rot in seedlings
- [00:09:58.833]so the exact inoculation assay wouldn't necessarily
- [00:10:02.955]be the same as the one shown here that's focused on
- [00:10:07.819]introducing the pathogen to the hypocotyl,
- [00:10:12.319]there's a variety of ways you can do this
- [00:10:14.246]but you can see the results are from the Chilvers lab.
- [00:10:18.252]Again, the Control with healthy roots can be compared to
- [00:10:22.745]the seedlings inoculated with the different species,
- [00:10:26.657]and now in this case we can see that the Phytophthora
- [00:10:29.920]at this later growth stage, and in particular
- [00:10:33.020]in warmer temperatures, which was a much more
- [00:10:36.596]aggressive pathogen, than it was as a seed rot.
- [00:10:43.838]The Pythium species again showed a seedlings disease effect
- [00:10:49.260]the most common, the most prevalent Pythium showing
- [00:10:55.420]a seedling disease impact compared to the control,
- [00:10:59.832]but not as severe as the Phytophthora impact.
- [00:11:03.210]So this kind of information was able to be obtained
- [00:11:07.610]because of the way they worked with a variety of isolates
- [00:11:11.291]that they collected from across the United States
- [00:11:13.833]soybean growing regions, and they were able to get answers
- [00:11:18.930]about specific species in terms of, do they cause disease,
- [00:11:23.156]how aggressive are they, and how are they interacting
- [00:11:26.651]with temperature differences.
- [00:11:28.613]So, the next questions they were interested in then,
- [00:11:32.432]is getting a better understanding of what the fungicide
- [00:11:36.438]response of the different isolates would be
- [00:11:38.806]and we'll tackle that in the next part
- [00:11:41.918]of our learning environment.
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