Term of Award

Summer 1992

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)


Department of Biology

Committee Chair

Sara Neville Bennett

Committee Member 1

Wayne A. Krissinger

Committee Member 2

James B. Claiborne

Committee Member 3

Donald J. Drapalik


Ten colonial mutants, H-1, pk, SS-129, col-1, col-6, col-12, spco-4, spco-7, smco-1, and smco-4, of N. crassa were observed to have little or no mycelial pigmentation when grown under constant light conditions. However, the mycelia of these ten mutants, when grown in the dark and followed by light irradiation, displayed pigmentation within 3 hrs. With the exception of smco-1 these strains also displayed pigmentation when they were grown in lower levels of light followed by exposure to increased light intensity. The degree and hue of pigmentation was specific for each strain. These pigmentation responses were also observed in cultures grown in liquid media.

Scanning electron microscopy of the ten mutants revealed increased branching in comparison to the wild type strain, 74. The pattern of branching also differed from that of the wild type and was acute lateral near the hyphal tips or else terminal. The hyphae were very dense and usually raised off of the medium. Although the morphology of all the mutants differed from the wild type, there was also variation among the ten mutants in the branching patterns and growing fronts.

The two traits, morphology and pigmentation, each showed 1:1 segregation and co-segregated in the eight mutants which were analyzed genetically and were pleiotropic effects under single gene control. Since in the mutants, morphology has been shown to be controlled by seven different genes, H-1 and pk being alleles, it would appear that there are several controls of the pigmentation phenomenon.

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