Preparation of pycnidium-forming fungi for observation by scanning electron microscopy
A procedure for the preparation of pycnidium-forming fungi, inside host tissues, for observation by scanning electron microscopy (SEM) has been developed, and consists of removal of mucilage from the pycnidium followed by fixation, embedding, and precision sectioning of pycnidia before final SEM preparation. The fungus tissues were fixed in glutaraldehyde and uranyl acetate. Tissues were prevented from collapsing by using glycerol substitution followed by air drying. The total procedure allows for direct comparisons, using the same sections, for light microscopy and SEM. Six species from the order Sphaeropsidales (Septoria avenae, S. avenae f, sp. triticea, S. nodorum, S. tritici, Darluca filum, and Phoma medicaginis) were used as experimental organisms; although only two species, S. avenae and S. tritici are pictorially represented.