Soybean Disease Diagnostics Lab

Don Lee Author

05/16/2016 Added

93 Plays

Description

For more information about Oomycete Disease Diagnostics visit the website: https://ge.unl.edu/oomycete-disease-diagnostics/

Searchable Transcript

Search:

[00:00:08.298]My name is Kevin Korus,
[00:00:09.715]and I coordinate the Plant and Pest Diagnostic Clinic,
[00:00:12.295]which is located in Plant Sciences Hall, Room 448
[00:00:15.255]on east campus at the University of Nebraska, Lincoln.
[00:00:17.653]And the clinic is setup to process all different kinds
[00:00:20.554]of plant samples from anywhere
[00:00:22.133]in the continental United States.
[00:00:23.573]So we can do turf, grass, trees, landscape ornamentals,
[00:00:27.053]fruits, vegetables and row crops.
[00:00:29.013]Most of my plant samples are row crops
[00:00:30.653]that come from Nebraska including:
[00:00:31.931]wheat, corn and of course soybeans.
[00:00:35.000]Early on in the soybean cropping system,
[00:00:36.900]we do have many samples submitted.
[00:00:39.200]And a lot of the time the clients are interested
[00:00:41.640]in understanding whether or not their stand reduction
[00:00:44.399]was do to either pythium infection
[00:00:46.260]or a phytophthora infection.
[00:00:48.098]Identifying a disease based simply on symptom expression
[00:00:50.996]is just not feasible.
[00:00:52.376]It can be dangerous, you may get a misdiagnosis.
[00:00:55.496]So we encourage plants be sent to the diagnostic clinic.
[00:00:58.456]So that in the clinic we can use our tools
[00:01:00.575]to go in and specifically find those causal agents.
[00:01:04.254]Specifically find pythium or phytophthora,
[00:01:06.495]so we can say with confidence, yup this pathogen is here,
[00:01:09.455]you have to deal with it now in your growing conditions.
[00:01:13.095]When samples arrive to the clinic,
[00:01:14.554]the first thing I do is take a look at what the symptom
[00:01:16.675]distribution is like on the plant.
[00:01:19.255]In general, pythium will attack the roots.
[00:01:22.474]And the very lowest roots will be affected:
[00:01:26.054]will be brown, will be discolored and maybe you'll see
[00:01:29.515]root schlepping, when the root cortex pulls off,
[00:01:32.054]and the root steels left behind.
[00:01:34.554]Phytophthora on the other hand,
[00:01:36.275]even though that particular organism
[00:01:37.655]does also infect the roots,
[00:01:39.355]it works it's way up into the crown and lower stem of the
[00:01:41.454]plant a lot quicker.
[00:01:42.814]And we often see darkening and discoloration of the lower stem
[00:01:46.175]and crown when we have phytophthora.
[00:01:48.555]However, if these symptoms aren't really obvious
[00:01:50.595]on the plant, we may need to try to isolate
[00:01:53.795]from these plants and try to obtain a pure colony of that
[00:01:56.854]particular micro-organism causing the problem.
[00:02:00.234](water pouring)
[00:02:08.535]So the idea of using isolations for identification
[00:02:11.555]of plant pathogens is that
[00:02:13.435]if there is a plant pathogen present,
[00:02:15.674]that pathogenic organism is invading the plant tissue.
[00:02:19.055]It's inside those plant cells.
[00:02:20.815]And it's protected from the outside environment.
[00:02:23.434]What we want to do is try to get at that one organism
[00:02:26.475]and isolate it artificially,
[00:02:27.975]so it grows in culture here in the lab.
[00:02:31.412]What we don't want are all of the other organisms
[00:02:34.510]that are on and inside the plant not causing any disease,
[00:02:38.811]but are just kind of there hanging out.
[00:02:40.450]We don't want them isolated onto our plates
[00:02:42.530]because that's just going to confuse our diagnosis.
[00:02:44.910]So what we do is a surface sterilization
[00:02:47.685]with a 10% bleach
[00:02:49.925]and 70% alcohol solution
[00:02:53.262]that we mix 50/50.
[00:02:54.787]The idea is if there is a pathogen present,
[00:02:57.500]it's inside the plant and it's protected from that solution.
[00:03:00.584]So we'll take a large chunk,
[00:03:03.376]and we'll just place it
[00:03:07.827]right into this solution for 30 seconds.
[00:03:12.508]After 30 seconds,
[00:03:15.067]the root sample gets a 30 second wash
[00:03:18.287]in sterile distilled de-ionized water.
[00:03:22.906]After 30 seconds,
[00:03:26.666]the root sample is placed on a sterile dry paper towel.
[00:03:30.566]So, the next part is basically placing this plant material,
[00:03:33.746]which is now sterile, onto media.
[00:03:38.182]And the media types differ depending on whether we are doing
[00:03:41.123]a pythium or phytophthora isolation.
[00:03:44.383]For each isolation, there is a
[00:03:46.203]selected media for each specific organism.
[00:03:48.602]For pythium isolations, we have a pythium-selected media
[00:03:52.682]on which the root sample will be placed.
[00:03:55.482]We also place the root sample on water auger,
[00:03:58.483]so an auger that contains no nutrients.
[00:04:00.503]And the purpose of this auger is that fungi and water molds
[00:04:03.522]will sporulate when they run out of a food source.
[00:04:06.703]So if we put them on water auger containing zero sugars
[00:04:09.362]or zero nutrient sources,
[00:04:11.223]it'll encourage them to sporulate quicker.
[00:04:14.023]And as soon as they sporulate then we can identify them.
[00:04:16.661]So the sooner they sporulate,
[00:04:18.060]the sooner our turn around time is here in the lab.
[00:04:20.920]Since the plant sample is already sterile at this point,
[00:04:23.741]anything we do, any utensil that we use that touches
[00:04:28.041]this plant material, must also be sterile.
[00:04:35.536]So we don't need very much.
[00:04:37.976]What I do is I cut the tip of the root off.
[00:04:41.276]Then I'll cut three or four smaller sections of the root.
[00:04:50.795]And opening the plate as quickly as possible.
[00:04:59.316]After the sterile pieces of root material
[00:05:01.056]are placed on the media, we seal the plate with peri-film
[00:05:04.535]to make sure that no fungal spores enter in.
[00:05:08.836]It'll take anywhere between three to seven days
[00:05:11.176]for that organism to grow out and then sporulate.
[00:05:14.596]The sporulation is key.
[00:05:16.676]We use the spores to be able to identify and differentiate
[00:05:19.755]between different genuses and species of plant pathogens.
[00:05:24.135]Within a week, we should usually have spores on our plate.
[00:05:27.835]And what I can do is I can take that plate and flip it over
[00:05:30.895]and stick it on a microscope and look at it at 200 X.
[00:05:34.515]And I can see right through the media.
[00:05:36.295]If there are any spores that have developed,
[00:05:39.011]I can identify which species they belong to.
[00:05:42.990]So it's really important for a producer to get a diagnosis,
[00:05:45.591]a firm confident diagnosis,
[00:05:46.950]because you can't start the correct management plan
[00:05:50.730]until you have the proper diagnosis.
[00:05:53.170]And if you try to manage a disease that is not there,
[00:05:56.710]you can end up doing more harm.
[00:05:59.130]Or you could be spending money in areas
[00:06:01.150]where you don't need to be spending money.
[00:06:02.830]So again, you don't want to âŚ
[00:06:07.030]you don't want to get a false negative diagnosis,
[00:06:10.270]and treat for something that is not there, and you don't
[00:06:13.348]want to not treat for something that is there.
[00:06:15.868]Again, so it's just simply putting into place the
[00:06:20.048]strategies that will mitigate the problem
[00:06:22.148]that you actually have.
[00:06:23.568]And that starts with the proper diagnosis.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Soybean Disease Diagnostics Lab

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments