Understanding Genes and the Environment



Two new scientific articles help explain how DNA, which makes up our genes, and the environment work together to express those genes. It was thought that humans had over 3 million genes, but now estimate that it closer to 300,000 genes. Microbes which live in humans and in plants supply the majority of the genes that control many life functions. Scientist are finding that the genes humans and plants obtain from their parents or “heredity is nothing more than stored environment” according to Luther Burbank.

Farmers can see this relationship when they plant the same seed in different fields with different soil types, and the crop expresses itself differently. This effect is compounded as multiple generations are grown in different environments. This same process expresses itself in the organisms we call ‘diseases’ or ‘pests.’ Sometimes a disease organism is not really a pest if it is in a healthy soil environment. The soil environment often determines which genes are expressed.

For example, fusarium populations typically cause disease in wet compacted soils but in healthy soils instead develop a symbiotic or beneficial relationship with the plant. The DNA or genes of the fusarium remains unchanged, but its expression is completely different. Other examples include foxtail seed, which if planted into a healthy soil that is well aggregated and has plenty of oxygen, will not even germinate. Lambsquarter, a common weed, cannot thrive in a forest soil because it is the wrong environment.

Insects will attack unhealthy plants but not healthy plants. Not all insects serve as vectors for viral diseases. If an individual insect benefits 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 often wreak havoc on one plant 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’.

Healthy plants in healthy soils resist disease. 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’s because our management practices have created a hospitable environment. Change the environment with adequate nutrition and microbial management to create a healthy soil, and you change your susceptibility to that disease. Adapted from an article by John Kemp. 

The second insight came from a newly released article in Science. Modern corn production and high yields comes from hybrid vigor. Researcher found that crossing two inbred lines of corn resulted in increased crop health, hardier plants, better growth and higher yields. In the 1940’s, corn regularly yield 25 to 40 bushels but since the 1940’s, corn breeders have increased yields dramatically by planting hybrid corn. Scientist recently discovered that this hybrid vigor is influenced by soil microbes which may affect a plants immune system.

The reason why hybrid corn yields more than inbred corn had been a mystery. University of Kansas, Dr. Maggie Wagner investigated the theory that beneficial soil microbes that live on the plant roots and leaves and protect against disease causing organisms might be the explanation. They discovered that different colonies of microbes lived on inbred corn lines than those living on hybrid corn. In their tests, they grew both hybrid and inbred corn lines in sterile soil, and the yields were similar. When they added beneficial microbes, only the hybrid lines increased yield. A hybrid corn variety reacts differently. Researchers think the inbred lines may retard plant growth rather than giving corn hybrids a boost. Another explanation is that corn hybrid plants may be better able to defend against soil pathogens. Scientist are currently researching these explanations.

The key point is that healthy soil microbes make agriculture more productive and sustainable. Creating a healthy soil environment with diverse microbial populations is the best way to get higher crop yields and to reduce pests. Most weeds have found a niche, growing in unhealthy soils, while some weeds cannot even tolerate or even live in well aggregated healthy soils. Insects which are normally pests, do not transmit disease or hurt healthy plants. Disease organisms may not hurt plants in a healthy soil environment, and may even become beneficial to the plant. Healthy soil and healthy diverse microbial populations create healthy plants, animals, and humans.