Introgression

Introgression, in genetics (particularly plant genetics), is the movement of a gene (gene flow) from one species into the gene pool of another by backcrossing an interspecific hybrid with one of its parents. An example of introgression is that of a transgene from a transgenic plant to a wild relative as the result of a successful hybridization leading to intentional or unintentional "genetic pollution", and another important example has been studied by Arnold & Bennett 1993: irises species from southern Louisiana.

But there are evidences that the introgression is a ubiquitous phenomenon in plants, even in animals and perhaps it also exists among pre-human lineages (Holliday 2003 ).

An introgression line (abbreviation: IL) in plant molecular biology is a line of a crop species that contains genetic material derived from a similar species, for example a "wild" relative. An example of a collection of ILs (called IL-Library) is the use of chromosome fragments from Solanum pennellii (a wild variety of tomato) introgressed in Solanum lycopersicum (the cultivated tomato). The lines of a IL-Library covers usually the complete genome of the donor. Introgression lines allow the study of quantitative trait loci, but also the creation of new varieties by introducing exotic traits.