Date of Award
Doctor of Philosophy
Reid G. Palmer
The development of a soybean (Glycine max (L.) Merrill) genetic map is an ongoing process. Formulae to calculate expected critical genotypic and phenotypic F[subscript]2 ratios were developed to facilitate the mapping of codominant markers by using primary trisomics. A method is given for calculating the minimum family size required to distinguish between a critical and noncritical segregation ratio when three phenotypic classes are present;The five known soybean primary trisomics A, B, C, D, and S were tested for linkage with 10 isozyme loci. Only one locus was assigned to a chromosome. The Dial (diaphorase) locus was located on the extra chromosome in Trisomic D;By analyzing segregating F[subscript]2 populations. the isozyme marker, Idh1 (isocitrate dehydrogenase), was mapped to linkage group 11. The gene order on this linkage group was F-Idh1-Rj1. In a similar study, a new linkage group was found. Pgi2 (phosphoglucoisomerase) was linked to the W4 locus with a distance of 44.8 ± 2.2 centimorgans;An independent area of research was the analysis of three different chlorophyll-deficient mutants (CD) derived from the w4-m soybean line that contains a transposable element. The w4-m line has flowers with purple sectors on a near-white background. Each of the CDs were a pale-green color and lacked the same two mitochondrial malate dehydrogenase enzymes. Allelism tests indicated each of the CDs contained a mutation in the same chromosomal region. The CD mutants and T253 (y20-k2) from the Soybean Genetic Type Collection were allelic. The yellow-green phenotype and the MDH-null were inherited as single recessive alleles. The plant color was stable even when the plant had mutable flowers. Therefore, neither a receptor nor a regulatory element was producing the mutant phenotypes. The CD mutants probably contain deletions involving the Y20 and MDH loci. The different phenotypes of the CD mutants suggest that the deletions have different endpoints. The deletions were not large enough to affect the transmission of the aberrant chromosome through the male and female gametes.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Bradley Robert Hedges
Hedges, Bradley Robert, "The application of primary trisomics and transposon-induced mutations in genetic studies of soybean (Glycine max (L.) Merr) " (1989). Retrospective Theses and Dissertations. 9192.