allele: form of a gene responsible for the coding of a single trait, such as herbicide resistance.
backcross: the resultant offspring from breeding a= hybrid back to one of its parents.
backcross generation: the number of times the same parent is used in a cross after the initial cross. For example the BC2 generation indicates one of the parents was crossed two additional times in that line.
biotype: naturally occurring individuals within the same species that differ in appearance and/or genetics.
gene: basic unit of inherited biological information; the portion of a strand of DNA that carries the code for a single protein or enzyme.
gene flow: movement of genes between plant populations.
genome: the complete set of DNA for an organism.
herbicide group: herbicides that act similarly on weeds; herbicides with the same fundamental biological action or site of action.
herbicide resistance: the inherited ability of a biotype to survive and reproduce following exposure to an herbicide applied at a rate that would kill the susceptible biotype.
herbicide rotation: changing the herbicide group used in a field from year to year to deploy different sites of action to minimize the potential for selection for herbicide resistance.
hybridize: crossing between varieties or species of plants to produce offspring.
Integrated Weed Management: the incorporation of all appropriate management techniques including biological, chemical, mechanical, and cultural practices in a weed control program.
mutation: random change in the genome of an organism; the result of either internal accident (a copying mistake during reproduction) or external causes such as exposure to mutagens.
natural selection: when an allele (trait) increases in a population due to pressure from the environment favoring that allele over another allele, resulting in an increase in individuals carrying the favored allele in the next generation.
nucleotide: one of the building blocks of DNA that consists of a phosphoric acid group, deoxyribose, and one of four bases: adenine (A), thymine (T), cytosine (C) or guanine (G).
out-cross: a plant that can be fertilized by another plant’s pollen; the offspring resulting from crosspollination.
plant population: a group of plants living in close proximity, under the same conditions.
selection pressure: impact of an environmental factor on the genetic composition of a population.
self-pollinating: a plant that can be fertilized by its own pollen.
semi-dominant: when a plant is heterozygous (has 1 copy of an allele) for a trait and the plant’s expression of that trait is approximately half of what the expression for the trait would be when the plant is homozygous for the trait (has 2 copies of the allele).
site of action: the place in a plant where a specific herbicide works.
Cover photo provided by Carol Mallory-Smith, Oregon State University.