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.