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Environment determines genetic expression

Prior to the human genome project, the popular expectation was that understanding the structure of DNA, and being able to edit or manipulate it’s structure would enable us remove the cause of degenerative illness.

As this project approached it’s concluding stages, it became obvious that DNA did not contain enough information to describe all the variability found within a given population. From this insight emerged the concepts of genetic fluidity and the science of epigenetics.

Epigenetics is the study of heritable changes in gene expression that do not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype. A foundational premise of epigenetics is that changes in environment result in changes of how an organism expresses itself.

“Heredity is nothing more than stored environment.” Luther Burbank

As farmers, we recognize this as an obvious truth. We know that we can plant the same seed in different fields with different soil types, and the crop will express itself differently. This effect is compounded as multiple generations are grown in different environments.

It is easy to recognize this process in plants, and also in animals.

We may not have appreciated enough how fundamental this process is in determining the pathogenicity or infectious capacity for the organisms we call ‘diseases’ or ‘pests’.

When we plant a blueberry plant into soil that is optimally balanced for alfalfa, we have placed it in an environment where it is unlikely to do well.

If we were to plant lambsquarter seeds into forest soil that is undisturbed, they will not even germinate, because they are not in the proper environment.

If we were to plant foxtail seeds into soil that is aggregated and well aerated, they also will not germinate, because they are not in the right environment.

Each of these examples is a case where the environment has determined genetic expression.

Soils can contain fusarium populations that are able to cause disease, but instead develop a symbiotic relationship with the plant, when there is a healthy soil microbial environment present. The DNA of the fusarium remains unchanged, but it’s expression is completely different.

Aphids will die in minutes, and become ‘candied’ when the sugar profile within plant sap they are feeding on changes. A change in the environment determines whether they live or die.

Not all insects in a given population serve as a vector for viruses. If an individual insect benefited from an optimal diet and environment, it will resist viral infections and not spread viruses from one plant to another. (Disease resistance is as real for insects as plants or animals)

Powdery mildew infections can decimate one variety, and leave another variety in close proximity completely untouched. The powdery mildew organism is present in both varieties, but one variety does not present a hospitable environment, and the organism never expresses itself as a ‘disease’.

We could continue this list until we included every ‘disease’ and ‘pest’ that is known.

The concluding point is simple: Every ‘pest’ requires a certain environment to be able to express itself. Change the environment, and the ‘pest’ ceases to be a problem.

If our crops are susceptible to disease or insects, it is because of our management practices that have created a hospitable environment. Change the environment with nutrition and microbial management, and you change the susceptibility.

 

Powdery mildew resistance on butternut squash

It would be common for organic butternut squash in Pennsylvania to be shutting down from powdery mildew pressure by mid-September. While neighboring growers had crops that collapsed completely, we could find no powdery mildew in this crop at all. The grower credited foliar applications of SeaShield, Micro 5000, HoloCal, MicroPak, and SeaStim for the plant health and vigor we observed in this 2017 crop.

2020-08-13T05:51:04-05:00August 13th, 2020|Tags: , |

Field results of nutrition management on freeze resistance, bacterial canker and powdery mildew in cherries

From the podcast interview with Mike Omeg:

John: Mike, you’ve been talking about the returns in very abstract terminology of return on investment, etc. Tell us about results. What has changed with your trees? We started this conversation by mentioning a desire to develop the root systems. What has changed with your root systems? What has changed with tree health? What have you actually observed in the field?

Mike: I have some anecdotes and then I have some actual data to share. Let’s start with the anecdotes.

In November of 2014, we had one of those once-in-a-lifetime historic freezes. The lowest the temperature had been was 43 degrees. Our trees generally go into dormancy in November, but it had been a very warm fall and the trees were still actively growing. We hadn’t had any acclimation to the cold. Then we had an arctic front come down, and we went from lows in the 40s to below zero in one day, and it stayed below zero. Here at my house, we had -4 degrees Fahrenheit.

The leaves on the trees just turned black. Just like a dahlia plant looks after the first frost, the leaves turned black, and they just hung on the trees. Several hundred acres of trees in our area just died. We had blocks where all the buds were frozen on the trees.

At that time, I was doing some comparison and analysis between mulch and intensive bionutrient applications and conventional applications for management of the orchard. I had two orchards that were sitting within a quarter-mile of each other at the same elevation. One was on one side of a small canyon and one was on the other. They were the same age and variety of trees and had the same irrigation. The only difference between them was the nutrition management. One had received compost mulch and bio-intensive nutrition, and the other orchard was just a standard conventional orchard.

After that freeze, all the trees in the conventional orchard were dead. They froze and the entire canopy was killed. We could have regrown them from the roots, but the trees were dead down to the soil. The entire orchard was smoked. There wasn’t one tree left. When you went and cut bark, it was black underneath instead of bright green. I had to remove that orchard the following spring

The orchard where we’d been following these bio-intensive practices, believe it or not, had 110 percent of a normal crop that year. We actually picked 10 percent more fruit out of that orchard than we did the previous year. That truly amazed me. That difference was only due to the nutrition management and these other activities that we were doing. There was no other difference.

The other thing that we’ve observed over time is a marked reduction in two pathogens that are problems for us with cherries. One of them is bacterial canker. Bacterial canker causes cherry trees to eventually die. They create a lot of gum. The trees get a canker that has a swelling of sap under the bark, and then these cankers burst, almost like a blister, and sap oozes out of them. That disease is a particular challenge with certain varieties and certain rootstocks of trees. If it doesn’t wipe the orchard out, it takes enough trees out that you lose the value of that block as an economic unit.

The consultants at Advancing Eco Agriculture I work with started to tell me that we should try to take on bacterial canker by focusing on nutrition. Over time we had an amazing transformation in a block that had significant amounts of bacterial canker—enough that I was going to take the block out. But I left it there because I didn’t have anything to lose.

Bacterial canker was actually eliminated from that block. It wasn’t just reduced—it was actually eliminated. Virtually all of the trees in that block had one or more canker sites on them. Some were far worse than others, but almost every tree had at least one canker on it. By the third or fourth year, we could not find bacterial canker in that block. I had neighbors coming to the block. I had extension staff and research pathologists from Oregon State coming to that block, and they could not believe the change.

The second disease that is more problematic in cherries is powdery mildew. That disease affects the foliage and fruit. It’s a real challenge. Powdery mildew is the disease that is targeted by almost all the fungicide applications that are applied in conventional and organic production of cherries. What we’ve seen is that highly susceptible varieties normally would require extra powdery mildew applications. But we’ve been able to reduce our applications by half, and maybe I could reduce them by more—I’m just a bit nervous about reducing them by more. But we have been able to apply half the number of fungicides to those trees, and we have no mildew there.

This is another thing that neighbors couldn’t believe, so we actually had a walking tour through that block. One of them was hosted by extension. I made a bet with the neighbors—I said, “Find any mildew in this block and I’ll buy you a steak dinner.” I’ve never had to buy a steak dinner because folks can’t find mildew in that orchard. A typical orchard with that variety in it would have lots of mildew because even with fungicide applications we are not able to control it.

Those are two things that that we’ve observed that I honestly thought would never happen. Through nutrition, we’re able to manage our diseases—in this case, with bacterial canker, and with powdery mildew. It speaks to the long-term value to the orchard of providing the nutrition that the tree needs. Do that and the tree will take care of itself.

P.S. I am hosting a Zoom video AskMeAnything discussion on Friday at 1 PM EDT. You don’t need to register in advance, just connect here at 1 PM.  See you there!

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