Degree Type


Date of Award


Degree Name

Doctor of Philosophy




An accurate, efficient method of screening the many germplasm sources for their ability to improve elite, adapted germplasm is needed. The superiority measure of population P was defined as the frequency of alleles in P weighted by their superiority over the best allele in an elite, adapted single cross I1 x I2. Three statistics were examined in terms of their expected correlation with the superiority measure. Under the assumptions made, the testcross to the elite single cross (TC SC ) was expected to be more highly correlated with the superiority measure than was a statistic proposed by Dudley (SD = P x I1 - I1 I1 x I2 - I2 - P x I2 - I2 I1 x I2 - Ia / 2 I1 - I2 ) or the upper bound (UBND = minimum P x I1 - I1, P x I2 - I2 ). The TC(SC) would require fewer testing resources than the other two methods, and would be expected to have a lower standard error. Another statistic proposed by Dudley (SD(,I) = I(,W) x I1 + I(,W) x I2 - I(,W) - I1 - I2 - I1 x I2 /4) for evaluating inbred I(,W) was expected to be more highly correlated with the superiority measure for inbreds than were the TC(SC)d and UBND. These two methods might have other advantages when evaluating inbreds. For example, fewer testing resources are needed compared to the SD(,I). Using a model of multiple alleles and four types of gene action (additive, dominant, complementary, and duplicate), screening methods for populations were examined using computer simulation. Positive correlations between products of allelic frequencies and effects at the different classes of loci in the simulated populations resulted in the UBND being in general more highly correlated with the superiority measure than the other two methods examined. It was usually not significantly more highly correlated with the superiority measure than was the TC(SC). The SD was in some cases negatively correlated with the superiority measure. Information used in calculating the UBND may be of special interest to breeders, although the TC(SC) may be an easier screening method and will require fewer resources.



Digital Repository @ Iowa State University,

Copyright Owner

Jane Ellen Gerloff



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174 pages