Term of Award

Spring 1992

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Sara Neville Bennett

Committee Member 1

Wayne A. Krissinger

Committee Member 2

Michael Moulton

Abstract

Growth characteristics were determined for wild type, 74A,Neurospora crassa on media with increasing osmotic pressure. Increasing the osmotic pressure of W-M medium with NaCI, KCI, or glucose decreased the biomass and the rate of hyphal elongation. The number of conidia and ascospores germinating decreased whereas the time interval between inoculation and initial germination of wild type conidia and ascospores increased with increasing NaCI concentrations. On media with increased osmotic pressure, two isolates 27A and 24C, exhibited osmotic-resistance by having more biomass, a faster rate of hyphal elongation, and a higher number of conidia germinating with a shorter interval between inoculation and initial germination of conidia.

J-12, a new mutant strain of Neurospora crassa.was isolated after UV irradiation of wild type conidia. This strain differed in morphology from the wild type strain by producing abundant conidia on a very reduced mycelium. It thus resembled the crisp mutants of Neurospora. Crosses of J-12 to the wild type strain allowed the recovery of progeny of two mutant strains indicating that J-12 was a double mutant. One mutant designated J-138 differed in morphology from both parental strains and additionally was osmotic-sensitive, failing to grow on media containing elevated concentrations of salt (6% NaCI). Crosses of J-138 to wild type resulted in 1:1 segregation of mutant and wild type progeny, with the traits of morphology and osmotic-sensitivity co-segregating. This indicated that the traits were due to a single gene under Mendelian control. J-138 was mapped to the right arm of Linkage Group I linked to arg-13 with 2% recombination. A three point cross of arg-13 to the double mutant J-138, un-18 placed J-138 to the left of arg-13 and crosses to os-1 produced no recombinants supporting allelism of the two mutants.

The other mutant designated J-6 had the crisp-like phenotype expressed in J-12 and when crossed to wild type produced progeny that segregated in a 1:1 ratio. J-6 was mapped to the right arm of Linkage Group III linked to ad-4 by 19.2% recombination. It is proposed that this new crisp mutant of N. crassa be designated cr-5.

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