Differential attachment by conidia of the endophyte, Discula umbrinella (Berk. & Br.) Morelet, to host and non-host surfaces.

Differential attachment of conidia to leaves of different species (host and non-host) has been observed in the endophytic fungus, Discula umbrinella (Berk. & Br.) Morelet, a deuteromycete known to cause occasional epidemics of anthracnose in beech stands. On beech leaves, attachment gradually increased over 24 h and reached a maximum after 16-24 h; there were small differences in attachment between conidia suspended in water and those in HEPES buffer. The range of variation of results obtained with conidia suspended in HEPES was smaller but the adhesion was clearly enhanced. The adhesion of conidia to the host surface was highest at pH 5, and decreased with increasing pH. Heat and chemical treatments significantly reduced attachment. Two factors (or groups of factors) are likely to be involved in the recognition process. The first is heat-labile, the second one could be a non-protein molecule present on the conidial surface and actively recognized by the host. The physiological similarity between endophytes and other symbionts is briefly discussed.