Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Professor S. F. H. Threlkeld


The purpose of this study has been to genetically analyze the aerialogenesis steps during differentiation of the fungus, Neurospora crassa. A new technique was derived for collecting data relating to the extension growth of aerial hyphae. This study comprised over 325,000 observations of aerial extension growth of over 46,000 colonies. These data were then analyzed by several new methods to characterize the aerial growth of the strains involved on medium containing 1% sorbose. Due to the large number of observations, a computer analysis procedure was utilized with the data. Once the phenotypes had been qunatitatively described, hypothesized genotypes and the variant alleles segregating could be accurately followed.

At least four genetic loci were observed to affect aerialogenesis in the presence of sorbose. Three of these loci were present, in two allelic forms each, in the original strains. A variant allele at fourth locus arose spontaneously during the course of this study. Several allele interactions have been characterized and some information is presented on gene locations.

The question of the relationship between aerialogenesis and conidiogenesis was also considered. No effects were seen on the qualitative aspects of conidiogenesis (macro or microconidiation). However, in several asci, distinct quantitative effects on conidiogenesis were observed segregating as expected of nuclear genes. In these asci, the quantitative changes in conidiogenesis were not correlated to quantitative changes in aerialogenesis. Hence, it appears that these two important development events can be separated genetically.

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