Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The interrelationships among agronomic, protein quality, and kernel quality characters in opaque-2 maize (Zea mays L.) require consideration of multiple traits in selection. Data from genetic studies in an opaque-2 maize synthetic were utilized to calculate selection indices for use in recurrent selection. Grain yield was considered the only trait having economic value. Restricted indices were used to achieve satisfactory gains in kernel hardness, moisture content and protein content and quality;The most important traits with respect to achieving the specified selection goals were yield, moisture content, kernel hardness, lysine content, kernel weight and the degree of light transmission by kernels. Indices incorporating five traits were the most efficient in that the addition of a sixth trait contributed very little to expected gains. The most effective combinations of traits for the recurrent selection scheme involving S(,1) testing were also the most effective for full-sib testing and S(,2) testing;The degree to which gains predicted for an index were dependent on accurate estimates of the population parameters was considered. Indices having weights that implied reliance on correlated rather than direct selection response were not recommended;Substitution of single plant data for data from replicated progeny tests was considered in connection with each breeding scheme. The possibility of increasing the effective selection intensity, given that resources for replicated testing were fixed, by culling individual plants was investigated, but the disadvantages of utilizing single plant data appeared to outweigh the advantages.



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Steven Kenneth St. Martin



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215 pages