Selective cross-breeding

Mike Lassner (Verdia Inc.) presented examples of the usefulness of directed molecular evolution as an in vitro process that more easily achieves what was traditionally attempted via reproductive crossing and recurrent selection (plant breeding). Proteins may be engineered that have specific desirable characteristics via methods that "evolve" the basic underlying DNA. For example, the outcome can be enzymes with improved kinetic properties that result in enhanced primary production, or proteins that remain operational under extreme conditions. In addition, compositional proteins may be enhanced to provide functional performance that was not achievable via conventional methods. 

Hybridization The production of offspring (hybrids) from genetically unlike parents, by natural processes or by human intervention (i.e., artificial selection). In plant breeding, includes the process of cross-breeding two different varieties to produce hybrid plants. If the hybrid is more fit than either parent the condition is called hybrid vigor (or heterosis). Hybrid offspring may result from gene flow between domesticated crops and wild relatives. 

Magnussen, S., and A.D. Yanchuk. 1994. Time trends of predicted breeding values in selected crosses of coastal Douglas-fir in British Columbia - a methodological study. Forest Science 40 663-685. 

Haploids can be produced from tetraploid cultivars and breeding clones via parthenogenesis (Hougas and Peloquin, 1957). When a tetraploid is crossed with any of several selected diploid clones, some of the offspring are diploid. In these crosses, both sperm cells from the pollinator enter the central cell, allowing normal endosperm to develop. This stimulates the division of the egg cell in the absence of fertilization, resulting in the production of a haploid (2x) embryo... 

Organic plant and animal breeding uses classical methods of crossing and selection based... 

Plant breeding the purposeful manipulation of plant species in order to create desired genetic modifications for specific purposes. This manipulation usually involves either cross- or self-pollination, followed by artificial selection of progeny. 

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