The appressoria formation of Colletotrichum graminicola was monitored by scanning electron microscopy (SEM) coupled with an X Ray microanalysis system (EDS - Oxford Instrument LINK ISIS). Recently formed appressoria, an infection structure of plant pathogenic fungi, firmly glues itself to an artificial surface (polystyrene) as a consequence of the production of an adhesive material (AM). The nature of this material was already demonstrated to be mainly constituted of a glycoprotein (Sugui et al, PMPP, 1998). The objective of this work was to verify the involvement of divalent ions, specially calcium, in the process as whole.
The AM was isolated and purified from conidia that germinated on polystyrene Petri dishes. The primary AM was dialyzed against three liters of distilled water before being lyophilized. Subsequently, the material was placed on top of a carbon tape and observed by scanning electron microscopy under high vacuum (Fig. 1 and 2A). On the other hand, the same material was submitted to X Ray microanalysis without coating.