Horacio Lopez-Nicora

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66 appearances 1 recordings 1 series first heard Mar 2025 last heard Mar 2025

Horacio Lopez-Nicora’s voice in public audio — every appearance, attributed to the second.

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Farm4Profit Podcast · Soybean Cyst Nematode: The Silent Threat Stealing Your Yield · 3 Mar 2025 podcast

Yes, it's a plant parasitic nematode. That's how we're going to call it. And not only that, we can add obligate parasite. It requires a living root to survive and to reproduce. You take the nematode out of that root that it's feeding on, and it will not survive. You try to grow it on something that is not alive, you will not be able to grow it.

Yeah. Thank you for having me. My name is Horacio Lopez-Nicora. I'm the soybean pathologist and nematologist here at The Ohio State.

So, yeah, like Dylan mentioned, there's several hypotheses of how it's moving so fast because The fact that it's moving, it makes sense. We move soil around, it's going to move around. So equipment that we don't clean very well, it's going to move the nematode around. You know, it sticks to the soil and anything that can move that will move the nematode. But how did it? move so quickly, right?

How did it expand throughout North America so quickly? And a different hypothesis is that it can also travel through that digestive system of these migratory birds. These may be picking, you know, roots and particles of soil that may contain those cysts, which are the dead females that contain the eggs. And these will survive through that digestive tract, and they will be dispersed.

That's another hypothesis, right? But one thing that, you know, we were talking at the beginning is that, I mean, this is an animal, like us. It's an animal, and it penetrates the root system and overtakes the plant machinery, right?

If we go and make thin cuts from those roots where the nematode is feeding, because it feeds from particular cells that it modifies, so it turns those cells into feeding sites. And if we make very thin sections and look it under the microscopes, those cells are completely modified, resembling transfer cells. I mean, these are not cells that we are supposed to find in the root system of any plant.

They're cells that we're supposed to find in the embryo, in the seed. So the nematode is really taking control of the plant machinery and making it believe that in my root system, that's where you need to feed your progeny. I mean, of course, I'm making these extremely more simple than what it is, but we don't see symptoms.

Like Dylan say, we have beautiful soybean plant losing 30% yield, and we just thought we had the best season of our life. And we left, you know, on average, what, $300 an acre below ground?

That's a great question. We have a physical damage, which is a penetration of the nematode. It has a stylet that we'll use to break into the cells and the root system, migrate to the vascular cylinder of the plant, where you have the phloem, where you have the xylem. So movement of water and nutrients are going up and photosynthates are coming down.

And the nematode sets these feeding sites very close to that region. So double punch there, right? But more of the damage is caused by these modified feeding sites. And it's way more intricate than just saying, you know, it modifies a cell, right? There's evidence of research of, you know, taking control of hormonal system, right?

So some of the major hormones like auxins will be up and down regulated. So it's fascinating, right?

Yes, it's a plant parasitic nematode. That's how we're going to call it normally. And not only that, we can add obligate parasite. It requires a living root to survive and to reproduce. You take the nematode out of that root that it's feeding on and it will not survive. You try to grow it on something that is not alive, you will not be able to grow it.

Very differently than with other pathogens of soybeans that we deal with, right? You mentioned SDS, for example. It's caused by a fungus. That fungus can be easily grown in a media that is not alive. It's still a parasite. It can parasite the plant. but still you can grow it on a media that is not alive. Soybean is an obligate parasite.

That's a great question. The mechanism of interaction is something that we are still trying to better understand. So the reports that we have and the evidence of interaction are... from very indirect observation. What does that mean? Well, when we have them both together, we see more SDS symptoms showing up.

Or SDS symptoms, which are those intervenial chloroses yellowing in between the veins of the leaf, show up earlier when we have a lot of nematodes. Understanding how that really happens, which is a mechanism, is still something that we're trying to figure out.

Yeah, that's a great question. And so the nematode will penetrate the root. So sometimes we think, you know, that resistance will avoid the nematode penetrating the roots, and that's not the case. So you put a tomato root and the soybean seed nematode will go inside that root. It will penetrate.

It will use the stylet, which is like a needle that it has on the head, to break those cells and migrate to the vascular cylinder. When the nematode penetrates a susceptible soybean, and does this migration to the vascular cylinder to establish this feeding site, it will probe cells with that stylet. It will release effectors, right, to engage in that interaction of host pathogen.

When that happens, the nematode becomes sedentary and cannot move anymore. And that's how it's going to complete its life cycle. The susceptible soybean will feed the nematode for its entire life. Now, at one point, the males will regain this warm light condition, will get out of the root and will fertilize females. The males won't feed anymore. At least we don't have evidence that they feed.

They will fertilize a female. This is a sexual obligate parasite, just like we are. We have to have sex to reproduce. Soybeans is nematode, have to have sex to reproduce. Now, this is very important because every sexual recombination means that there is a possibility to shift virulence, to adapt to new traits, to become more resilient.

So this is great from the perspective of the pathogen that can adapt very well. Now, what happens when we have a resistant soybean? the nematode will penetrate the root of a resistant soybean, will migrate to the vascular cylinder, will start probing those cells and engage in this interaction with this plant.

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