Methods of reducing variability in the results of glass‐slide spore‐germination assays of fungitoxicity

Abstract

SUMMARYWhen conidial spores of Venturia inaequalis (Cooke) Wint. were germinated on glass, in distilled water only, very little variation was found, but addition of copper sulphate produced a marked variation, particularly between slides.An examination of the standard cleaning technique showed its inadequacy to produce a chemically clean surface, but the introduction of a cleaning method based on permanganic acid led to a very marked decrease of the total variation.When copper sulphate was applied as a deposit, with various wetting agents, to slides cleaned by this method, there was no appreciable reduction in the variation. When the wetting agent was applied with the spore suspension, however, a marked reduction was obtained, but the total variation was further reduced to an acceptable level only when the toxicant was applied in the nutrient solution in which the spores were suspended.A modification of a commercial inverted microscope, to facilitate counting, is described.

Bioassay as a monitoring tool

“…Test-tube dilution methods (with extract) provide easy approaches to a standard curve. FRICK (1964) specifically discussed methods of reducing variability in the results of glass slide spore germination assays of fungitoxicity and that discussion is useful for the bioassayist. This is a sensitive assay procedure, simple in its general outline but requiring careful controls of the organism source, culturing conditions, temperature, and other variables (NEELEY 1969).…”

The value of in vitro fungicide tests

“…Comparisons of Methods of Tesfina-There have been relatively few published reports in which the methods for determining fungitoxicity have been compared. In obser\ations of techniques invohing spore germination, Frick (1964) found the test tube dilution test less variable than the dried deposit-slide germination test. Gottlieb ( 1945 ) found the seeded, toxicantagar method and the test tube dilution method equally sensitive.…”