title: Sources of variability in the measurement of fungal spore yields.
abstract: VARIABILITY IN THE PRODUCTION OF FUNGAL SPORES AND IN THE MEASUREMENT OF SPORE YIELDS WAS INVESTIGATED IN FOUR SPECIES OF FUNGI: Colletotrichum gloeosporioides, Colletotrichum coccodes, Colletotrichum phomoides, and Acremonium strictum. When the fungi were grown on solid medium in microplates and spore yields were measured by counting the subsamples with a hemacytometer, the variability among hemacytometer squares was always the largest source of variation, accounting for 51 to 91% of the total variation. Variability among replicate cultures and results of repeat experiments were generally also significant. The effect of square-to-square variability on the precision of spore yield measurement was minimized by counting a moderate number (ca. 30) of squares per culture. Culture-to-culture variability limited the practical precision of spore production measurements to a 95% confidence interval of approximately the mean +/- 25%. We provide guidelines for determining the number of replicate cultures required to attain this or other degrees of precision. Particle counter-derived spore counts and counts based on spore weights were much less variable than were hemacytometer counts, but they did not improve spore production estimates very much because of culture-to-culture variability. Results obtained by both of these methods differed from those obtained with a hemacytometer; particle counter measurements required a correction for spore pairs, while the relationship between spore weights and spore counts changed as the cultures aged.
authors.affiliation: Department of Plant Pathology, Departments of Forestry and Statistics, Department of Botany, and Department of Soil Science, University of Wisconsin-Madison, Madison, Wisconsin 53706.
authors.forename: C S
authors.initials: CS
authors.lastname: Smith
authors.forename: S J
authors.initials: SJ
authors.lastname: Slade
authors.forename: E V
authors.initials: EV
authors.lastname: Nordheim
authors.forename: J J
authors.initials: JJ
authors.lastname: Cascino
authors.forename: R F
authors.initials: RF
authors.lastname: Harris
authors.forename: J H
authors.initials: JH
authors.lastname: Andrews