Co-Authors:
Rotem, J., Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, SA 5064, Australia
Clare, B.G., Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, SA 5064, Australia
Carter, M.V., Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, SA 5064, Australia
Abstract:
Optimum wetting periods for sporulation of Rhynchosporium secalis in barley leaf lesions incubated at 5, 10, 15, 20, 25 and 28°C were 72, 72, 48, 24, 16 and 12 h, respectively. Lysis of previously formed spores occurred when wetting periods exceeded those which were optimal for sporulation at any given temperature. Both continuous wetting periods and interrupted wetting periods of the same total duration had similar effects. Lesions caused by R. secalis contained saprophytic bacteria of which a green, fluorescent pseudomonad was the dominant species. When bacteria isolated from leaf lesions were added to water on which sporulating leaves were floated, lysis of spores was enhanced. This lysis was partly inhibited by chloramphenicol. Cell-free diffusates from sporulating leaf lesions and from Pseudomonas sp. cultures enhanced lysis of previously formed spores. Spores were completely lysed by diffusates from leaf lesions whereas diffusates from bacterial cultures caused lysis of protoplasts but not of spore walls. These effects increased with increase of wetting periods and were more pronounced at 20 °C than at 10 °C. Addition of bacteria without diffusates to suspensions of spores from cultures did not result in lysis. It is postulated that more than one agent is needed to lyse both the protoplasts and the walls of spores and that the combined actions of these agents precondition the spores to further destruction by bacteria. © 1976.
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