Backcrossing

Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent. It is used in horticulture, animal breeding and in production of gene knockout organisms.

Backcrossed hybrids are sometimes described with acronym "BC", for example, an F1 hybrid crossed with one of its parents (or a genetically similar individual) can be termed a BC1 hybrid, and a further cross of the BC1 hybrid to the same parent (or a genetically similar individual) produces a BC2 hybrid.

York radiate groundsel (Senecio eboracensis) is a naturally occurring hybrid species of Oxford ragwort (Senecio squalidus) and common groundsel (Senecio vulgaris). It is thought to have arisen from a backcrossing of the F1 hybrid with S. vulgaris.

Again, the pure tall (TT) and pure dwarf (tt) pea plants when crossed in the parental generation, they produce all heterozygote (Tt) tall pea plants in the first filial generation. The cross between first filial heterozygote tall (Tt) pea plant and pure tall (TT) or pure dwarf (tt) pea plant of the parental generation is also an example for the back-crossing between two plants. In this case, the filial generation formed after the back cross may have a phenotype ratio of 1:1 if the cross is made with recessive parent or else all offspring may be having phenotype of dominant trait if back cross is with parent having dominant trait. The former of these traits is also called a test cross.

In plants, inbred backcross lines (IBLs) refers to lines (i.e. populations) of plants derived from the repeated backcrossing of a line with artificially recombinant DNA with the wild type, operating some kind of selection that can be phenotypical or through a molecular marker (for the production of introgression lines).

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