Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Detroy E. Green


A three year study was conducted in which the objective was to determine the response in seed yield from a tandem selection scheme in which the first step was to select desirable lines from each of two single cross populations for morphological and developmental traits, using independent culling. The second step was to select for high plant nitrogen (N) content at the R5 developmental stage. The genetic material was 213 F6 derived indeterminate lines from three maturity groups (79 early, 93 medium, and 41 late lines) from a single cross population (IX139) and 102 lines from three different stem termination types (28 determinate, 40 semideterminate, and 34 indeterminate lines) from a different cross (IX149);Yield increase from the first part of the selection scheme in the early, medium, and late maturity groups of IX139 was 2.2, 1.9, and 5.6%, respectively with a mean of 3.2% across locations and years. Selection for morphological and developmental traits in the determinate group of IX149 decreased the seed yield by 4.6% and increased the seed yield in the semideterminate and indeterminate groups of IXl49 by 1.1 and 4.9% across locations and years. In the second portion of the tandem selection scheme, selection for high plant N content at R5 decreased the seed yield by an average of 0.3% across the maturity groups of IX139 and increased the yield by 1.4% across the three stem termination types of IX149;In assessing the overall response to tandem selection in all groups within IX139 and IX149, most groups responded positively, but the determinates decreased in seed yield by 4.1%;Plant nitrogen content at the R5 stage, because of its low association with seed yield and the inconsistent seed yield response to selection does not appear to play a significant role in determining the final yield.



Digital Repository @ Iowa State University,

Copyright Owner

Hassan Zeinali-Khanghah



Proquest ID


File Format


File Size

128 pages