Date of Award

Winter 1992

Project Type

Dissertation

Program or Major

Plant Science

Degree Name

Doctor of Philosophy

First Advisor

Yun-Tze Kiang

Abstract

Genetic variation is the basis of crop improvement. As genetic background narrows in the cultivated germplasm, genes need to be introduced from new sources. Glycine soja is a wild relative of the cultivated soybean, glycine max (L.) Merr. It can be used in soybean breeding. Evaluation of wild soybean populations is not only necessary for use in cultivar improvement, will also provide information about origin, migration, evolution and natural selection of this species. Seeds were collected from six natural populations in South Korea to study the genetic variation and differentiation of wild soybean.

The study was divided into two parts: (a) lab assay for 17 isozymes and one protein involving 35 loci; and (b) two-year greenhouse experiment, during which data for morphological traits were recorded.

The average number of alleles per locus, 99% polymorphism and the expected heterozygosity in the total population were 2.1, 77.1% and 0.215, respectively. Nei's gene differentiation (G$\sb{\rm ST}$) was 0.383. The average Nei's genetic distance was 0.117.

Populations were not significantly different in mean CV (coefficients of variation) for both years. However, 27 of the 33 individual morphological traits examined in 1989 and 31 of the 39 in 1990 differed significantly among populations. The average among-population variation per trait per degree of freedom was 84.38% in 1989 and 83.11% in 1990.

Although there were no significant differences among populations in mean CV, those populations with high genetic variation also had high mean CV for morphological traits. There was no congruence between the isozyme and morphological data in terms of population relationships.

Multilocus association analysis provided significant insight into the genetic structure of these natural populations. The analysis indicated that within each population, there were two to three dominant multilocus genotypes. The multilocus genotypes were "biotypes" at the morphological level. These different types might be the basic genetic division of mosaic self-pollinated plant populations, and the basic units in natural selection and evolution. The analysis also suggested that there was no migration among these six populations in recent history.

The numbers of loci different between individuals were used as measures of genetic variation and genetic distance.

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