Glossary

• Bacillus thuringiensis (Bt) is a species of bacteria that is naturally occurring in soil. It makes proteins that are toxic to some insects when eaten, but not others. The proteins are not toxic to humans because, like all mammals, we cannot activate them. Bt is used as an insecticide and it must be eaten to be effective.  Spores of Bt are widely used in organic gardening. Bt corn is a genetically modified variant of corn that has been altered to express one or more proteins from the Bt bacteria. The Bt protein is expressed throughout the plant and when a vulnerable insect eats the Bt-containing plant, the protein is activated in the insect’s gut. The insect stops eating within a few hours and eventually starves.

• Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique.

• Cisgenic: if a gene transferred into a plant came from a different species, the result is commonly called transgenic (or GMO) If it is from the same species, it is called cisgenic. Cisgenic gene transfers are done when a particular variety of the species adapted to one location contains a gene that would be useful to a variety adapted to another location. For example, a plant growing in the tropics may have a disease resistance gene that would help protect plants growing in temperate climates.

• CRISPR-Cas9 is a unique gene-editing tool that enables plant breeders to edit part of a plant’s genome by removing, adding, or altering sections of the DNA sequence. The CRISPR-Cas9 system has two parts that introduce a genetic mutation into a piece of DNA: a piece of RNA called guide RNA and an enzyme called Cas9. The guide RNA is developed to find and bind to only a targeted sequence of the DNA to be changed. This guide RNA leads the Cas9 enzyme to the spot and the enzyme works like scissors to snip both strands of the DNA at that exact point. The cell recognizes that its DNA has been damaged and tries to repair it. Scientists use this DNA repair process to introduce changes in one of more genes. The CRISPR system was originally discovered as a natural way that bacteria defend themselves from attacks by viruses.

• Cross-breeding and subsequent selection is used by plant breeders to create new genetic variants and leverage existing genetic diversity. The breeding and selection process takes many generations to achieve plant hybrids and varieties that look, smell, taste and yield in a more reliable and predictable manner. Although each crop breeding effort may have unique practices, their selection methods and goals are the same: improving plant productivity, quality or quantity. Society has benefited for thousands of years from the genetic changes humans have made to plants.

• A cultivar, also known as a variety, is a combination of plants selected for desirable characteristics that are maintained during propagation. A cultivar is the most basic classification category of cultivated plants. For example, a single soybean variety that is distinct, uniform and stable, would be considered one cultivar.

• Deoxyribonucleic acid (DNA) is a molecule that carries genetic instructions for the development, functioning, growth and reproduction of all known living organisms. DNA and ribonucleic acid are nucleic acids. All living organisms contain DNA as the basic building block of their characteristics.

• Doubled haploid is a process which enables breeders to develop a true, genetically uniform, inbred more quickly and efficiently. A doubled haploid is a parent line which only has one set of chromosomes, vs the normal two sets. These are called haploid plants. The number of chromosomes is then doubled again to create a genetically uniform (homozygous) plant. Doubled Haploids are valuable in research and development because scientists can develop 100 percent genetically pure plants in just two generations, compared to the usual seven generations. This increases the speed and efficiency of breeding. Doubled Haploids can be used to study traits and as inbred lines in breeding.

• Embryo rescue refers to a number of lab techniques whose purpose is to promote the development of an immature embryo into a viable plant. Just like say chicken eggs, seeds have an embryo as well; which is the part of the seed that eventually becomes a plant (the rest of the seed is for protection and to feed the embryo). Embryo rescue is widely used to rapidly speed up the time from one plant generation to the next. Additionally, certain plant characteristics can be selected during the embryo rescue process, significantly reducing the number of different plants that need to go to the field for evaluation.

• A  gene  is the basic physical unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify traits. Genes are arranged, one after another, on structures called chromosomes.

• Genetically modified organisms (GMOs) or Transgenics in agriculture, are products developed using certain biotechnology tools, commonly defined as when a gene is transferred from one species to another .  Most of the GMO traits on the market today are designed to help protect crops from being eaten by insects or being overrun by weeds, helping farmers produce more on each acre of land with fewer inputs while ensuring a stable and sustainable food, feed, fuel and fiber supply.

• Genome (or gene) editing allows breeders to make precise changes to the genetic code. Until recently, our ability to modify the DNA of an individual plant or animal in a targeted way was limited. We could use the processes of crossing and selection over multiple generations and hope to create the right combination of genes, or we could transfer one or a few genes using biotechnology. With the advent of genome editing technology, breeders are developing plants to have beneficial traits such as better nutrition, expanded shelf life, faster growth, higher yield, and greater tolerance to droughts, extreme weather and disease. These DNA changes could occur in nature or be developed through conventional breeding but genome editing makes it possible to deliver them faster and more efficiently, with breeders using knowledge about the function and characteristics of genes and how they may contribute to the phenotype of the plant. Please see our gene editing section for much more information on CRISPR-Cas.

• Guide RNA is one of the parts of the CRISPR-Cas9 system to do precise editing of a plant’s DNA.  See CRISPR-Cas9.

• A  hybrid  plant is created when plant breeders intentionally cross two different varieties or inbreds to produce an offspring, that is stronger and performs better than either of the parents. Cross-pollination is a process that occurs within members of the same plant species. Hybridization occurs both in nature and through human intervention.

• An  inbred  line consists of plants that are self-crossed to create genetic uniformity, as the start of the hybridization process. These inbred lines are selected to serve as parents for new hybrids based on complementary traits, such as yield, stress tolerance, and/or pest and disease resistance. Plant breeders combine valuable traits from each parent to generate and select offspring containing the best characteristics of both parents. For example, breeders are often trying to improve certain weaknesses that exist in one parent with complementary strengths in the other parent.

• Introgression is a term in genetics used to describe the movement of one gene from a genotype into another (often a more advanced, elite line) for the purpose of improving that one specific characteristic. This is accomplished by repeated crossing with a target variety.

• Molecular Markers are used by plant breeders to genetically map the genome of a crop species. Molecular markers are unique sections of DNA which are associated with particular traits. They are situated along the genome, and provide a view of the genetic makeup in that specific region. Scientists use markers to screen for the presence of traits even before the plant is fully grown. There can be thousands of molecular markers for any single crop species. In fact, the more markers available to scientists, the better they will be able to screen for traits before the plant is ever grown in the field.

• Mutagens are physical or chemical agents that can cause changes to the genetic material. An example of a mutagen is the ultraviolet rays of sunlight that alter or cause mutations in genes of plants. Another specific example of a natural mutation is in the waxy gene in certain corn lines which result in a type of corn plant with a starch composition that makes it suitable for a wide variety of special uses, from food-grade corn starch to glossy coatings. At Corteva, we recently developed a new generation of waxy corn using gene editing.

• Natural mutations occur in nature as a result of sunlight and other factors that interfere with DNA’s ability to copy accurately. Human and plant cells mutate frequently. Evolution is the result of naturally occurring ongoing mutations. For example, when a cell divides, it makes a copy of its DNA, and sometimes the copy is not quite perfect. That small difference from the original DNA sequence is a mutation. Sometimes a mutation can be a disadvantage to a plant; other times it can be an advantage.

• Natural selection is a form of evolution. It’s a process where organisms better adapted to their environment tend to survive and produce more offspring. Naturally selected organisms tend to have some fitness advantage over others in a population. Alternatively, plant breeders practice intentional selection based on data and observations of some measured or estimated performance advantages.

• Natural variation, similar to genetic variation, refers to the diversity in genetic material of a population or species. Plant breeders leverage natural variation to select for desired characteristics in a breeding population.

• Phenotype is the term used for the composite traits of an organism. The term covers the organism's morphology, or physical form and structure, as well as its developmental processes, biochemical and physiological properties and behaviors. In humans, a phenotype might describe height or weight , physical strength or a simple characteristic, such as eye color.

• Pollination is the process of a male plant or flower (or part of a flower) fertilizing the female part of that same species. In nature this happens by wind, bees, bats, insects, etc., or sometimes close proximity of the male part of the flower producing pollen to the female portion containing the embryo. In all cases it results in fertilization of the embryo and ultimately in developing a seed. When plant breeders carry out pollinations, or cross pollinations, they are simply collecting the male pollen and manually placing the pollen on the receptive female portion of the flower. Plant breeders sometimes use automated methods of collecting the pollen and distributing on one or many females. For a plant breeder there are two primary purposes of making cross-pollinations: 1) to make hybrid seed for testing, evaluation and eventual commercial sale of the best performing hybrids; or 2) to make a breeding cross that produces offspring for selection of higher performing off-spring.

• Tissue culture and regeneration is a step in the biotechnology process. After a gene is transferred from the cell of one plant species to another, the newly transformed cells are used by scientists to cultivate living plant tissues in the lab. They then provide the plant tissues with the right conditions to develop into seedlings. The seedling eventually grows into an adult plant with progeny seed that contains the transferred gene.