Host Infection in Pellicularia filamentosa controlled by Chemical Stimuli

Abstract

PATHOGENIC specificity of different strains of the fungus Pellicularia filamentosa (Pat) Rogers to different host plants has been shown by Flentje¹ to be determined at two distinct stages in the infection process. One of these stages is on the external surface of the host stem before penetration occurs. The hyphæ of a pathogenic strain become attached to the cuticle of a susceptible host above the junction of epidermal cells, grow in a characteristic manner along the stem following the lines of junction of these cells, and form complex appressoria or ‘infection cushions’. Each infection cushion is produced from a side branch in which normal elongation has ceased but in which further prolific side branching has occurred. Infection takes place only from these cushions. Strains not pathogenic to the host fail to become attached to or organize on the stems. Flentje¹ suggested that this differential reaction may be due to a diffusible chemical exudation from the host.