Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)


Extensive breeding investigations with soybeans in this country have been under way for only a relatively short period of time. Breeding work was at first confined primarily to introduction and selection, but it was soon realized that the possibilities for continued improvement with these practices were definitely limited. Consequently, during the last 10 or 15 years, hybridization has rapidly supplanted these procedures as the principal means for obtaining new and improved varieties.

Methods of handling segregating populations of crosses in such self-pollinated crops as wheat, oats, barley and flax now are fairly well standardized. Practices involve various modifications of the pedigree method, the bulk method or a combination of the two. An advantage of the pedigree method is that it enables the investigator to conduct inheritance studies of characteristics in which the parents differ. The principal advantages of the bulk method are cheapness in cost and opportunity to conduct replicated bulk yield tests as early as the F2 generation. Early generation yield testing with the pedigree method, on the other hand, is limited or practically impossible in certain crops because of the scarcity of seed produced on individual plants and the high cost of testing large numbers of lines in replicated tests. Segregating populations of soybean crosses are admirably adapted for breeding by either of the two methods, as comparatively large seed yields on spaced individual plants make it possible to conduct pedigree yield tests as early as the F3 generation. Replicated tests for evaluation of agronomic potentialities of soybean crosses in early segregating generations following hybridization, therefore, can be used with either the bulk or the pedigree method of breeding.



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