Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Walter R. Fehr


Soybean [Glycine max (L.) Merr.] genotypes with reduced palmitate, stearate, and linolenate have been developed to improve the nutritional characteristics and oxidative stability of the seed oil. The reduction of palmitate and stearate in soybean is necessary to comply with U.S. Food and Drug Administration (FDA) regulations for vegetable oils that are labeled as being low in saturated fatty acids (U.S. FDA, 1994). The reduction of linolenate should improve the oxidative stability and reduce the formation of undesirable flavor compounds in the oil (Dutton et al., 1951; Smouse, 1979; Mounts et al., 1988; White and Miller, 1988);Plant-row-yield tests (PRYT) are used by soybean breeders for the initial yield evaluation of experimental lines. The highest yielding lines in the PRYT are advanced for evaluation in replicated tests. The objectives of this study were to compare the family and line methods of selection for reduced palmitate, palmitate + stearate (saturates), linolenate, and for increased seed yield, determine the influence of the combination of reduced palmitate and linolenate on agronomic and seed traits, and determine the effectiveness of selecting lines from unreplicated plots;Four random F3-derived lines from 21 F2 families from each of four populations were evaluated in a PRYT in 1995 and in replicated tests at four locations in 1996. For the family method, the mean palmitate, palmitate + stearate (saturates), linolenate, and seed yield of the four F3-derived lines of each F2 family was used to identify families from which to select individual lines. For the line method, lines were selected without regard to the family structure. The fatty ester contents or seed yield of the selected and unselected lines based on data from the PRYT were compared with their mean performance in the 1996 environments. Selection of lines based on data from one 1996 environment was compared with their mean performance in the other three environments. The total number of lines selected by the family method was less than for the line method for all traits in the four populations. The percentage of selected lines that were correctly classified for all traits was similar for both methods. There was a greater percentage of lines incorrectly rejected by the family method than by the line method for all traits. For development of cultivars with reduced palmitate, saturates, and linolenate, and with increased seed yield, breeding methods that rely on family performance would not be more effective or efficient than methods that ignore family structure. The evaluation of lines in unreplicated plots was useful for identifying lines to advance to replicated tests.



Digital Repository @ Iowa State University,

Copyright Owner

Leon George Streit



Proquest ID


File Format


File Size

164 pages