Ridell Method- Microscopy Stains and Techniques in Mycology

Slide Culture Preparations:

Note:In order to accurately identify many fungi it is essential to observe the precise arrangement of the conidiophores and the way in which spores are produced (conidial ontogeny). Riddel’s simple method of slide culturing permits fungi to be studied virtually in situ with as little disturbance as possible. A simple modification of this method using a single agar plate is described below. One plate of nutrient agar; potato dextrose is recommended, however, some fastidious fungi may require harsher media to induce sporulation like Cornmeal agar or Czapek Dox agar.

• Using a sterile blade cut out an agar block (7 x 7 mm) small enough to fit under a coverslip.
• Flip the block up onto the surface of the agar plate. 
• Inoculate the four sides of the agar block with spores or mycelial fragments of the fungus to be grown.
• Place a flamed coverslip centrally upon the agar block. 
• Incubate the plate at 26^OC until growth and sporulation have occurred. 
• Remove the cover slip from the agar block. 
• Apply a drop of 95% alcohol as a wetting agent. 
• Gently lower the coverslip onto a small drop of Lactophenol cotton blue on a clean glass slide. 
• The slide can be left overnight to dry and later sealed with fingernail polish. 
• When sealing with nail polish use a coat of clear polish followed by one coat of red-coloured polish.