Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Four sets of oat lines were subjected to selection for grain yield by using two stable and two disruptive selection strategies, and the surviving lines were evaluated for mean yield, yield response to improving environments, and stability of production. Stable-high and stable-low selection strategies were conducted by sequentially selecting the highest yielding lines in either continuously high or low productivity environments. After three or four cycles of selection, the surviving lines and a random sample from each set were evaluated in a range of environments typical of oat production on Iowa farms. A stability analysis was conducted on the grain yield data from each group of selected lines to compare the effect of stable and disruptive selection on the grain yield characteristics, mean yield, response to improving environments measured by regression, and stability of production measured by deviation mean squares or the coefficient of determination;Grain yield and regression response for all selection strategies, when calculated across sets of lines, were significantly greater than the corresponding means for the random sample. Stability was essentially unchanged. The stable-high and stable-low strategies gave the greatest and least gains in grain yield, respectively, with the disruptive strategies giving intermediate gains. Disruptive selection in predominantly high productivity environments was the more effective method for increasing grain yield at low and intermediate levels of productivity. The stable-high strategy followed by the disruptive-high strategy identified entries with superior performance in high productivity environments. Greater gain in grain yield was associated with increasing number of selection cycles conducted in high productivity environments;The effectiveness of disruptive selection cited by previous researchers was not found in this study, perhaps because the low and high productivity environments were not sufficiently diverse. The advantage of high productivity selection environments in a breeding program was demonstrated.



Digital Repository @ Iowa State University,

Copyright Owner

Carrie Young



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92 pages