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Date of Award


Degree Name

Doctor of Philosophy




Maximum genetic gain from recurrent selection requires an efficient and effective strategy for selection of superior individuals from a population and intermating the selections to form a new population. This research was conducted to compare alternative strategies of recurrent selection for seed yield in soybean Glycine max (L.) Merr. . Four strategies initiated in the AP6 soybean population represented a factorial arrangement of one or two stages of replicated yield testing before selection of superior F(,4)-derived or S(,2)-derived lines and one or three generations of intermating between cycles. A fifth strategy, representing a conventional breeding program, was initiated in a population formed by sampling the first of three generations of intermating used to synthesize AP6. The conventional breeding strategy utilized a two-stage yield test of F(,4)-derived lines obtained from a limited number of single crosses each cycle. Three populations of different maturity were maintained for each strategy. The response to selection was determined by evaluating composites of the parents of each cycle at three locations during 2 years. The number of cycles completed for the strategies varied from two to five. The genetic gain per cycle and year was greater for one generation of intermating than for three generations. The two-stage yield evaluation had greater gain per cycle and year than the one-stage yield test. The conventional breeding strategy had the highest yield and the greatest gain per cycle and year of all the strategies. Changes in maturity in response to selection were small. The response of height was not consistent across strategies and lodging tended to increase. The results indicate that a recurrent selection program utilizing two stages of yield testing and one intermating generation would be most effective for increasing seed yield in soybean. The superior performance of the conventional breeding strategy does not support the use of recurrent selection in a closed population for short-term cultivar development.



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Todd Elliott Piper



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101 pages