Seed Development in Modern Times

Seed Development in Modern Times

Posted by Uncle Buck on Jul 28th 2020

The understanding of inheritance, the flow of genetic information from one generation to the next, and of DNA’s role in holding genetic codes led to the science of biotechnology. As a result, hybrid seeds and genetically modified (GM) crops have surfaced as a powerful commodity throughout the world.

The Beginning of Biotechnology

It took 100 years to unravel the mystery of genes and form the study of biotechnology. It all started with Gregor Mendel (1822-1884) who developed the theory of genetics in 1865 by breeding pairs of pea plants of contrasting characteristics. He developed the Punnet Square, still used today to predict heredity and the passing of genetic traits, to understand the role of inheritance and exchange of genetic information from one generation to the next. In the early 1900’s, Thomas Hunt Morgan (1866-1945) discovered chromosomes and the genes they carry. He developed the theory of meiosis, the process of cell division and reproduction. He was the first to understand the DNA sequence which helped solve many questions relating to heredity. In 1944, Oswald Avery (1877-1955), leading a Rockefeller University research team, discovered that inheritable characteristics of cells are modified through DNA uptake called transformation.

A flurry of understanding followed suite, and DNA became the basis of all scientific knowledge and biological experiments. It was soon understood that through genetic manipulation organic cells can be persuaded to contain foreign DNA, a process called DNA uptake. By studying bacterial genetics scientists developed recombinant DNA technology, cloning and multiplying genetic DNA coding sequences and inserting them into unrelated hosts, resulting in genetically modified organisms (GMOs). And thus biotechnology was born.

Biotechnology Applied to the Seed

Hybrid Seeds

Artificially cross pollinating two plants to create an improved variety results in a hybrid plant variety. Understanding the genetic basis of inherited traits allowed scientists to realize they could breed two pure crop varieties together to produce predetermined characteristics in the following hybrid generation. The first attempt at hybrid crops was with corn. Two corn varieties were planted in alternating rows. When the corn had grown large enough scientists removed the tassels of one variety, only allowing pollen to be released into the field from the second variety. Seed from the first variety of removed tassels would produce hybrid seeds. Scientists first noticed that hybrid plants yielded more crops than their parent crops, a term called “hybrid vigor.”

Hybrid vigor was so enticing that scientists began “double-crossing” plants. Two inbred parents were crossed with two other inbred parent plants. Resulting hybrid crops were bred together one more time and produced seeds that grew plants with characteristics of all four parent plants. Double-crossing plants to produce hybrids was used from 1926 to the 1960’s until scientists developed better ways to create inbred lines with only one cross of parent plants in the lab.

Scientists have continued to inbreed plants with an aim at improving certain characteristics of the plant. Not only do biotechnologists breed for higher yield but also improved color, long shelf life, thick skins to endure cross-country shipping, and uniform appearance. Hybrid vigor is often believed to be the biggest factor in a dramatic rise in crop production in the second half of the 20th century and as a result hybrid seeds have become the dominate seed in both agriculture and horticulture. Due to significant inbreeding, hybrid seeds are sterile and don’t reproduce seeds that are true to type and look like their parent plants. As a result they must be purchased every year for replanting.

Genetically Modified Seeds

Genetically modified seeds are also called GMO or GM crops, abbreviations for the term “genetically modified organisms.” GM seeds are a result of recombinant DNA technology, genetically tampering with plant DNA to incorporate foreign traits and characteristics such as immunity to toxic herbicides and producing poisonous proteins that kill insects.

Biotechnologists have focused on developing plants that are genetically immune to herbicides and insects by introducing genes to plant DNA that make herbicides chemically inactive. Today plants are designed to survive against two major herbicide brands and stand against insects using genes from a pesticide.

  • Roundup-ready plants. Roundup-ready plants are those genetically altered to survive spraying the herbicide Roundup.Roundup is an herbicide that kills plants with the chemical glyphosate. Glyphosate interferes with the enzyme EPSP syntheses which makes 3 essential amino acids in the plant (tryptophan, tyrosine, and phenylalanine) that are needed for protein synthesis. Plants die without these amino acids. To make plants resistant to Roundup, Monsanto (the company that makes Roundup and sells GM Roundup-resistant seeds to famers) has cloned a gene that is resistant to glyphosate and transferred it into crops. Monsanto’s soybean was the first GM crop cultivated on a large scale that is resistant to glyphosate, also called Roundup-ready.
  • Liberity-link plants. Liberty herbicide uses a chemical called glufosinate to kill weeds. Glufosinate’s cellular enzymes convert to ammonia as nitrate is naturally absorbed from the soil. Ammonia is used by plant glutamine synthase to manufacture the essential amino acid, glutamine. Glusofinate inhibits the glutamine synthesis. Ammonia then builds up in the plant cells, and high concentrations of ammonia are toxic to all life. To make plants immune to Liberty herbicide, scientists developed an enzyme coded to chemically alter glyfosinate and inactive it, and inserted this enzyme into certain crop DNA.
  • Bt crops. Plants designed to carry pesticide within their genetic makeup are called Bt crops. Bt toxin is an insecticide that has been sprayed on crops for decades. Scientists have discovered how to clone the Bt toxin gene from the bacteria is derives from (Bacillus thuringiensis) and transfers it into plants. Bt toxins are proteins made by bacteria that degrades in the gut of insects and releases harmful fragments that are toxic to insect’s cells. It is believed that since humans have different types of proteins in their bodies and have different pH levels that Bt toxins do not harm the human digestive system.

Protection of Hybrid and GM Seeds

The US Supreme Court has ruled that hybrid and genetically engineered crops could be patented as propriety life forms. Plant Variety Protection (PVP) awards ownership and property rights of seed varieties to the companies or individuals that develop them. Certificates are now granted to protect hybrid varieties. This has changed the definition of seeds forever. Originally designed to assist global trade and encourage scientific innovation patents instead restrict the flow of genes.

This allows the companies investing in hybrid and GM seed development and marketing can own life and specific genes by law. Scientists can now insert genetic identifiers into plants that serve as markers in cellular structures serving as a signature to prevent unauthorized use of the seed or technology used to develop the seed.

Benefits of Seed Development

Economic Benefits

Hybrid and GM crops have the potential to offer economic benefits to farmers. Bred to produce higher yield and longer shelf life, hybrid seeds are also genetically modified to reduce insecticide costs, lower pesticide poisoning in the soil, provide efficient weed, pest and virus control, thus reduce labor and fuel costs.

Potential Future Benefits

Positive developments in the application of biotechnology to plants could potentially solve global agricultural and health problems. Hybrid vigor could be used to feed more of the crowded earth’s populations. By inserting fish antifreeze proteins into plants, scientists believe they could produce crops resistant to frost and cold weather. Nutritional enhancements could be made to food theoretically helping to reduce malnourishment in the developing world. This has been exemplified in the engineering of Golden Rice, a genetically modified rice variety designed to contain high levels of beta-carotene that could enhance the population’s Vitamin A intake.