Author Topic: Selecting for Nitrogen Fixing Roots in Corn / Maize  (Read 154 times)

Andrew Barney

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Selecting for Nitrogen Fixing Roots in Corn / Maize
« on: 2018-10-26, 08:16:51 AM »
So, i had heard that they had discovered nitrogen fixing corn on another forum, but i hadn't really looked into it much. It sounded slightly intriguing, but not completely surprising, but then i forgot about it. Then i listened to this awesome podcast!

https://www.talkingbiotechpodcast.com/154-nitrogen-fixing-and-corn/


Quote
photo attribution: Aerial roots of corn from Sierra MixeALAN BENNETT / UC DAVIS

https://www.theatlantic.com/science/archive/2018/08/amaizeballs/567140/

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2006352

First off the podcast was amazing! Second i realized that i have already observed this in some of the corn i have grown before. And on a purple stalked corn. Since i mostly grow "unimproved" indian corn it makes sense that i would encounter it more than say highly modern corn bred for indiana with high chemical fertilizers and highly inbred and low genetic diversity. So it's possible i already still have it in my purple corn population. I see areal roots all the time and they look slightly odd. Some varieties have more, some longer roots, and some less or shorter. The ones that tend to have lots of nodes and areal roots are the taller ones from mexico or south america since more roots stick out of the ground, so it's more noticeable. I remember seeing it because one day i was wondering about if i could make my own rooting powder or gel for my hard to root wild tomato cuttings. That is when i thought about growing my corn and chopping off some of those roots. I remember seeing one with gooey gel around the roots, and the roots were purple. I only recall seeing the gel on one, but the fact that i remembered it makes it exciting.

I have a theory that it is more common that these scientists think it is, but would be more common to older corn strains, indian corn, mexican, and south american corn. I have not selected for aerial roots or against them, but i remember thinking once that maybe they would look better without them. I'm glad i didn't select against them now. I'm thinking we should all start selecting for higher rates of gel producing aerial roots. They would tend to be the stronger more healthier plants in an organic or low fertilizer system anyway and so might naturally produce more seed over time. It's possible i have inadvertently selecting for this trait without even knowing it, just by saving the best seed.

has anyone else seen this trait amongst their corn?! Anyone else want to start selecting or observing for it?!

Joseph Lofthouse

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #1 on: 2018-10-26, 09:07:05 AM »
That article showed up on the forums I participate in just before I started harvesting my seed corn. Sitting here at my computer, I intended to screen every patch of corn for areal roots before harvest. Then I'd get to the field and harvest by my typical selection criteria. Therefore, of the 8 patches of corn I grew, I only harvested seed from the air-rooted plants in 3 of the patches.

All of my landraces have the air-root trait to some degree. It was highest in the progeny of the South American corns. The high-carotene flint corn had the highest percentage of air-roots. I saved a lot of seed from air-rooted plants.

The air-root trait produces a root ball that is dense and fibrous. It doesn't break up readily while tilling, and it doesn't decompose easily. I can understand why the trait has been selected against in North American commercial strains.




Andrew Barney

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #2 on: 2018-10-26, 09:29:19 AM »
That article showed up on the forums I participate in just before I started harvesting my seed corn. Sitting here at my computer, I intended to screen every patch of corn for areal roots before harvest. Then I'd get to the field and harvest by my typical selection criteria. Therefore, of the 8 patches of corn I grew, I only harvested seed from the air-rooted plants in 3 of the patches.

All of my landraces have the air-root trait to some degree. It was highest in the progeny of the South American corns. The high-carotene flint corn had the highest percentage of air-roots. I saved a lot of seed from air-rooted plants.

The air-root trait produces a root ball that is dense and fibrous. It doesn't break up readily while tilling, and it doesn't decompose easily. I can understand why the trait has been selected against in North American commercial strains.

Cool! Joseph,  how many of the air-roots actually have the gelatinous goo on them? I suspect just having aerial roots may only be half of the solution. Perhaps selection within those that have aerial roots should be done for those that have gel. Of course that gel might be environmentally driven,  so maybe not.

reed

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #3 on: 2018-10-26, 09:38:47 AM »
I thought pretty much all corn has aerial roots at least most I'v grown has, some more than others of course. Might they be environmentally encouraged to some degree?  The Zapalote Chico that I fell in love with this past season has lots.

I'v never noticed the goo, but I never thought to look for either, I will from now on.

Joseph Lofthouse

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #4 on: 2018-10-26, 10:28:11 AM »
I think that in my hyper-arid garden, that the occurrence of gel is environmentally driven. Perhaps more likely to occur during irrigation. Dew or rain are extremely rare here.

Ocimum

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #5 on: 2018-10-27, 06:19:49 AM »
Air roots in corn/sorghum are can be a sign of soil compaction or waterlogging. The plant (corn, sorghum, I do not know about others) reacts by developing the air roots, pneumatophores if I get it right.

Therefore, I am not sure if selecting for aerial roots is a good idea. Maybe selecting the leaf nitrogen content in poorly fertilised soil is better, as it does select for the plants who are: able to pick up nitrogen from the air, better at working with mycorrhiza, or work with symbiotic bacteria.

For example Joseph, you would have no use of aerial roots if the plant is not able to fix nitrogen without the gel on your fields. Or did I miss a point?

Here an example of a leaf nitrogen tester. Calibration is not needed as long as you always use the same tool.
https://www.yara.co.uk/crop-nutrition/farmers-toolbox/n-tester/

Joseph Lofthouse

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #6 on: 2018-10-27, 10:17:01 AM »

As a plant breeder, I select for what people want to grow. This year, that happens to be plants with areal-roots. It's like when people come to the farmer's market, and then ask me, "What do you do with XYZ vegetable?" The most accurate and honest response is: "I sell it at the farmer's market!"

To be fair to the corn, I spent less than 15 minutes paying attention to the air-root phenomena this summer. The day I inspected them, the few that I inspected, were not covered in mucus. There were a lot of plants, and a lot of environmental conditions that I didn't inspect. I did notice however that root-tips which hadn't penetrated the leaf yet were moist. Perhaps providing a place for the nitrogen fixing bacteria to thrive.

Traditionally, air roots have been favored by some plant breeders because they may provide increased anti-lodging, or anti-predation (same basic trait, if an animal can't pull a plant down, it might move along).
 

Andrew Barney

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #7 on: 2018-10-27, 10:58:14 AM »
Yes i also was thinking it could help against lodging which would be good. I hadn't even thought about anti predation,  but that would really help me out. Raccoons are a problem here.

Richard Watson

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #8 on: 2018-10-29, 08:22:04 PM »
Air roots in corn/sorghum are can be a sign of soil compaction or waterlogging.




No would not agree with that, ive garden in very friable free draining soil and get plenty of aerial roots in the past. I will be taking a lot more notice in this summer corn, it will be a mix of old and new varieties.
 

Andrew Barney

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #9 on: 2018-10-29, 10:11:38 PM »
No would not agree with that, ive garden in very friable free draining soil and get plenty of aerial roots in the past. I will be taking a lot more notice in this summer corn, it will be a mix of old and new varieties.

Richard, i think he or she might be referring to sorghum. Maybe it works different in sorghum. When i use the term "corn" i am using it in the American sense as in "Maize", not sorghum like in many other parts of the globe.

Richard Watson

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #10 on: 2018-10-30, 02:48:53 AM »
Thanks for pointing that out Andrew, i didnt know that.

reed

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #11 on: 2018-10-30, 02:53:50 AM »
I also don't agree on the soil compaction theory. Now that I think about it, some modern sweet corns I'v seen may not have the aerial roots but most corn I'v grown does. It can help lodging but only if they are nice and strong, originated four or five inches above the ground and are well anchored before a strong wind hit. We always just called them anchor roots or prop roots. A lot of corn has multiple tiers of them and some corn when it lodges just roots down and stands back up with the bottom having rooted down horizontally a foot or so on the ground.

It might just be a case of corn getting back to it's roots,so to speak. I don't know about other ancient teosinte but zea diploperennis I am fairly sure grows the air roots, possibly among other things as a means of propagating itself. Here is a section of stalk with the air roots growing at every single node. (sorry for the image quality, you have to look close) It is about four feet long and the cut end was another four feet off the ground.



It was tied up to a post so it couldn't fall over but others that did, rooted down and the side shoots grew into new stalks.

I'm still interested in the notion of nitrogen fixing but I have never seen the goo forming as in some of the pictures. It just occurred to me, might the air roots be epiphytic to a degree, like the spider plant (Chlorophytum comosum) I bring in each winter and almost never water? I'm told that z dip is native to cloud forest where it might easily extract water if nothing else from the air.

I'll keep watching this thread for any more info on the nitrogen fixing aspect but for me prop roots are prop roots. I like them if nothing else cause I think they are cool looking but I don't think I'll select for or against.   
« Last Edit: 2018-10-30, 03:08:28 AM by reed »

Oxbow Farm

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #12 on: 2018-10-30, 06:21:00 AM »
Its pretty impossible to say how common the nitrogen fixing symbiosis is amongst different corns, but I think aerial roots are incredibly common, and almost every corn I've added into my breeding projects has expressed it to one extent or another.  I also think the "gel" on the roots has more functions than feeding bacteria.  I also think the time when it is most visible to us is the period when nitrogen fixing is completely NOT its primary function.  The gel appears and disappears on the same roots based on the humidity conditions at that time of day.  On a dewy morning or right after a rain, they are covered in gel.  On a hot windy afternoon, the gel is completely invisible.  It is clearly a very hygroscopic, mucus-like excretion.  Its not clear to me if the plant produces fresh gel every time the conditions are right, or if the gel is always present but just rehydrates and dries out as the humidity changes.

I think that when the roots are above ground, the primary function of the gel is to lubricate the penetration of the root into the soil surface.  Once the root is below the surface, that's when the fixation symbiosis becomes relevant if the plant is capable of it (JMO).  All the plant/fungi/bacteria symbiotic systems I'm familiar with require structures with lots of surface area.  Aerial roots don't have any surface area to speak of.  If you dig up a root ball, you see that those aerial roots start branching immediately when they get below the soil surface. 

Ocimum

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Re: Selecting for Nitrogen Fixing Roots in Corn / Maize
« Reply #13 on: 2018-11-09, 03:02:36 PM »
I somehow posted the following message in a wrong category:

Quote
...Among the well enunciated roles played by ethylene in waterlogged condition, induction of gene expression linked to leaf senescence, aerenchyma formation, adventitious roots, and epinasty are paramount (Jackson, 2008; Vidoz et al., 2010; Sasidharan and Voesenek, 2015) as morphological responses. These responses were observed with concomitant increase in endogenous ethylene synthesis in crops, including maize, barley, wheat, and soybean (He et al., 1994; Watkin et al., 1998; Drew et al., 2000)...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5622204/

And about compaction and lateral roots: the study and the abstract
http://sci-hub.tw/https://doi.org/10.1016/0098-8472(91)90058-V