Advanced Backcross Breeding Glossary

allele

One of the different forms of a gene (or marker) that can exist at a single locus. A single allele for each locus is inherited separately from each parent.

backcross

A breeding method used to move one or a only a few desirable genes from an agronomically poor crop line to an elite line. This is done by crossing a donor parent to an elite line, and crossing offspring with the 'desired gene(s)' back to the elite parent.

backcross breeding

After a plant has been transformed, the event must be moved into an elite genetic background. This is done by mating the transformed plant back to elite plants over several generations.

backcrossing

A breeding method used to move one or only a few desirable genes from an agronomically poor crop line to an elite line. This is done by crossing a donor parent to an elite line, and crossing offspring with the 'desired gene(s)' back to the elite parent.

centromere

The region of the chromosome associated with the attachment of the chromatids to the spindle fibers.

character

A distinguishing feature or attribute of individuals, groups, or categories.

chromosome

A genetic structure in a cell composed of condensed DNA, which contains the genetic code for an organism.

chromosomes

The genetic structures in cells composed of condensed DNA ,which contain the genetic code for an organism.

crossing

The deliberate mating of two parental types of organisms in genetic analysis.

dominant

The allele that is expressed in a heterozygous organism.

donor parent

The parent from which one or a few genes are transferred to the recurrent parent in backcross breeding.

elite

A crop line that has many genes for good agronomic traits that result in high yields in a particular environment.

environment

The combinations of all the conditions external to the genome that potentially affect gene expression.

gene

The fundamental unit of heredity that carries genetic information from one generation to the next. A gene is an ordered sequence of nucleotides located on a particular position on a particular chromosome that encodes a specific functional protein.

gene stacking

Creating a plant with a desired combination of two or more unique genes. This can be done when the genes are first transferred into the cells by co-transformation, or during the breeding process by crossing two lines that each contain a different gene resulting in progeny with both genes.

genotype

The allelic composition of a cell or organism.

heritability

The proportion of observed variability which is due to heredity, the remainder being due to environmental causes. More strictly, the proportion of observed variability due to the additive effects of genes.

heterozygote

An organism having two different alleles at one or more locations.

homozygosity

Having like alleles at corresponding loci on homologous chromosomes.  An organism can be homozygous at one, several, or all loci.

homozygous

An organism that has two identical alleles at one or more locations on a chromosome. Inbred lines are homozygous at many of their gene loci.

hybrid

An individual produced by crossing two parents of different genotypes.

inbreeding

Mating between closely related organisms.

intense selection

Selection for the trait(s) of interest with little or no retention of lines not having the trait(s) of interest.

line

Plants within a species that have the same genetic composition and are genetically pure, (i.e., inbred line). Lines are typically not agronomically competitive and are used only in plant breeding.

lines

Plants within a species that have the same genetic composition and are genetically pure, (i.e., inbred line). Lines are typically not agronomically competitive and are used only in plant breeding.

linkage

The association of genes on the same chromosome. The shorter the distance between two genes, the greater the probability they will be inherited together.

meiosis

A type of cell division which results in the formation of gametes, cells with half the normal number of chromosomes.

nontarget genes

Genes in the recurrent parent that are not at the locus of the gene of interest. Basically, nontarget genes are all those genes in the recurrent parent that the backcross breeder would like to retain in the backcrossing program.

phenotype

The observable physical characteristics of an organism that are determined by a combination of the genetic composition (genotype) and the environment of the individual.

phenotypes

The observable physical characteristics of an organism that are determined by a combination of the genetic composition (genotype) and the environment of the individual.

progeny

The offspring of an organism.

progeny testing

A test of the value of a genotype based on the performance of its offspring produced in some definite system of mating.

qualitative characters

A character in which variation is discontinuous.

recessive

A trait that will not be expressed unless there are two copies of the gene allele present in an organism.

recombination frequencies/map distance

Recombination frequency is the frequency of crossovers between two genes. The map distance (in this case a genetic or recombinational map) is the recombination frequency between two genes times 100. For example, if the frequency of recombination is 0.10, the map distance is 10 map units.

recurrent parent

The parent to which successive backcrosses are made in backcross breeding.

resistance

The ability of an organism to survive and thrive in the presence of something that would normally cause damage or death, i.e., herbicide-resistant corn, Roundup-ready corn.

segregating population

A collection of lines from a cross or population that is undergoing Mendelian or Hardy-Weinberg gene segregation.

species

A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding.

tissue culture

Plant cells are grown in culture which allows them to be manipulated and then induced to develop into whole plants.

trait

The characteristic that results from an expressing gene(s). Ex. Upright leaves, drought tolerance, Bt resistance. A trait can be influenced by the environment.

transformation

A process by which extra genetic material is inserted into the cells of an individual.

transforming

The process of introducing foreign DNA into an organism which is then passed on to the organism’s progeny.

transgenic

An organism that has a new genetically engineered DNA sequence found in every one of its cells. Genetically engineered organisms are transgenic. These two terms are used interchangeably.

variety

Crop plants within a species that have the same genetic composition. Because plants in a variety are usually heterozygous, their offspring will not remain genetically pure (i.e., corn hybrid varieties).

yield lag

A relative reduction in yield observed in some hybrids or varieties compared with the yield observed in the most recently produced hybrids or varieties.