Plant breeding is the purposeful manipulation of plant species in order to create desired genotypes and phenotypes for specific purposes.
This manipulation involves either controlled pollination, genetic engineering, or both, followed by artificial selection of progeny.
Plant breeding often, but not always, leads to plant domestication.
Plant breeding has been practiced for thousands of years, since near the beginning of human civilization.
It is now practiced worldwide by government institutions and commercial enterprises.
International development agencies believe that breeding new crops is important for ensuring food security and developing practices through the development of crops suitable for their environment.
Classical plant breeding uses deliberate interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties.
Plants are crossbred to introduce traits/genes from one variety or line into a new genetic background.
For example, a mildew-resistant pea may be crossed with a high-yielding but susceptible pea, the goal of the cross being to introduce mildew resistance without losing the high-yield characteristics.
Progeny from the cross would then be crossed with the high-yielding parent to ensure that the progeny were most like the high-yielding parent, (backcrossing).
The progeny from that cross would then be tested for yield and mildew resistance and high-yielding resistant plants would be further developed.
Plants may also be crossed with themselves to produce inbred varieties for breeding.