Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Candice A. C. Gardner

Second Advisor

E. Charles Brummer


Molecular markers were utilized in conjunction with phenological and morphological information, and statistical methods for diversity analyses to address plant genetic resource conservation issues. The objectives of this study have been categorized into two sets. The first set pertains to exploratory surveys of genetic variation using molecular markers and DNA sequences to determine if microsatellite markers or variation in two copies of the FLOWERING LOCUS C gene (FLC1 and FLC3) can be used in determining life forms of fifty representative accessions of Brassica napus. The second set of objectives addresses good genebank practices and includes: characterization of flowering time of the spring-type B. napus without vernalization; assessment of the validity of bulking B. napus and B. rapa germplasm; and determining the effectiveness of isolation of B. napus accessions during caged germplasm regeneration. Use of a microsatellite set from 18 B. napus linkage groups and three expressed sequence tags (ESTs) grouped accessions based on life forms correctly. Eleven microsatellite loci were found to have significant association with flowering time. Analysis of the FLC gene copies indicated low nucleotide polymorphism in exons 4 to 6 in both annual and biennial types of the crop. A life form specific haplotype was not found in either copy of FLC analyzed. The curatorial concerns addressed by the second set of objectives were answered by utilizing a set of ten microsatellite markers, and by simple bioassay of a dominant herbicide-resistance trait. Information derived from the ten microsatellites was analyzed using assignment tests together with tests for population differentiation and cluster analysis of genetic distances. Results of this study indicated unique accessions among B. rapa bulks and in the B. napus putative duplicates. Reformulation of several bulks was recommended. The use of the herbicide resistance trait was found useful in testing the effectiveness of field cages during regeneration. The study confirmed that wind blown B. napus pollen can pass through the current screen mesh size used during regeneration and cause cross fertilization in adjacent plots, but at very low and tolerable level.



Digital Repository @ Iowa State University,

Copyright Owner

Von Mark V. Cruz



Proquest ID


File Format


File Size

137 pages