Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Plant, Soil and Environmental Sciences

Major Professor

Fred Allen, Milton Constantin

Committee Members

L. N. Skold, V. H. Reich


In 1979 seven dwarf plants were identified in segregating M3 generation progeny of the soybean (Glycine max, L. Merr.) cultivar 'Bedford' which had been treated with 0.05 M ethyl methane sulfonate (EMS). Seeds harvested from each of the dwarfs and from 10 phenotypically normal plants were used to establish M4 generation progeny the following year. Twenty normal looking plants were selected from each of the 10 segregating rows in 1980 and used to establish 10 families consisting of 20 subfamilies each in 1981. Counts were taken prior to flowering of dwarf and normal phenotypes within each subfamily. Nine families were found to be segregating for normal and dwarf phenotypes. The results obtained from these segregating families and subfamilies were used to evaluate the mode of inheritance of the dwarf mutant. The data were analyzed according to three different genetic models; a single recessive gene (3 normal:1 dwarf ratio); two genes with duplicate dominant epistasis (15 normal:1 dwarf ratio) and two genes with dominant and recessive epistasis (13 normal:1 dwarf ratio). The observed segregation ratios best fit the single gene model where dwarfness is recessive to normal. F1 progeny from artificial crosses between normal looking plants within and among families also supported this model. Data were taken on 10 Bedford dwarf and 10 normal plants in order to compare the morphology of the dwarf mutant with the normal phenotype. Results showed that the Bedford dwarf had rugose leaves and was about one third the height of Bedford. The dwarfing was from a shortening of internodes as well as from a reduction in number of nodes. Other characteristics such as number of pods per primary branch and main stem, length of internodes of primary branches and 100 seed weight were reduced compared to normal Bedford. However, the number of primary branches and the number of nodes per primary branch of the Bedford dwarf was greater than for normal Bedford.

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