As one of the most important agricultural crops in the world, supplying over 55% of the carbohydrates consumed by man, bread wheat has been the subject of considerable attention by geneticists intent on improving world food production. In past, Wheat chromosomes and genes have been manipulated far more than those of any other of the major world crops. Bread wheat is a polyploid species, which makes it very pliable for gene manipulation because it can tolerate a vast array of alterations in its genome without lethal effects on viability. Plants can stand the loss or addition of a chromosome or homoeologous pair, the deletion of whole arms or chromosome segments, and the insertion of alien gene complexes; and can still survive to produce seed. A common method used for alien transfer involves exposing wheat seed carrying a monosomic addition for the alien chromosome carrying a desirable major gene, to X-rays, to induce transfer of an alien segment to wheat chromosome.