Studies in the Genus Fusarium

Abstract

This paper records changes which have taken place in certain Fusarium strains during the course of continued culture on artificial media. Little evidence was obtained of any progressive changes brought about by selective culturing. Thus, apart from slight changes of a more or less ephemeral nature, it was immaterial whether successive generations of cultures were taken from spores only or from mycelium only. On the other hand, sudden changes arose from time to time in the form of saltations, a number of which are described and figured. Saltation was found to occur more frequently on a rich medium such as Richard''s solution than on the comparatively dilute nutrient medium described by the author. Thus it is suggested that for the purpose of keeping labile strains a dilute medium is desirable, whereas the same form can be made to saltate on a richer medium. When a labile form is cultured on the latter type of medium, there is considerable risk that a saltant portion may be transferred on reculturing, and so the original strain may be lost. Some of the Fusarium saltants possess diminished parasitic powers, and thus an explanation is suggested for the well known loss of virulence of parasitic organisms when kept in culture.