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Title: The behaviour of zoospores of Pythium species
Author: Donaldson, Stephen P.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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Pythium aphanidermatum (Edson) Fitz., Pythium catenulatum Matthews and Pythium dissotocum Drechs. were compared for responses to amino acids and sugars in tests involving taxis, zoospore encystment and cyst germination in vitro. Comparisons were made between the fungi and for each fungus at these three stages of development, which are parts of the normal sequence leading to infection of host roots or colonisation of non-living substrata from zoospores. Other substances tested for induction of encystment or germination in vitro were cellulose film, crab shell, uronic acids or uronate-containing compounds, partially characterised polysaccharides from plants, root mucilages and cations. Motility attributes of the fungi were compared and, for P. aphanidermatum only, were characterised in the presence of several ions and compounds that interfere with calcium-mediated events (EGTA, dibucaine, trifluoperazine, lanthanum, verapamil, amiloride, A3187 and TMB-8). Amino acids were tested for competitive effects in chemotaxis assays in vitro. Calcium and EGTA were also tested for effects on adhesion of encysted spores to glass slides. Accumulation and encystment of P. aphanidermatum on detached wheat roots was studied on microscope slides, with or without prior treatment of roots with calcium alginate gel, methylene blue, alcian blue, India, ink ruthenium red and lectins that bind residues of fucose, D-glucose, D-mannose, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. Many experiments involved video-recording zoospore responses and subsequent analysis of videotapes. Evidence is presented for an effect of calcium and other divalent cations on zoospore motility patterns, cyst adhesion and induction of germination. Several amino acids and sugars elicited zoospore taxis, encystment, or cyst germination but sometimes differently for different fungi or at these different stages of development. Competition experiments enabled some of these responses to be related to proposed receptor functions, and in some cases amino acids could overcome inhibition of germination caused by the presence of calcium-modulators.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available