FIELD-EMISSION GUN-SCANNING ELECTRON-MICROSCOPY OF SEPTAL PORE CAPS OF SELECTED SPECIES IN THE RHIZOCTONIA SL COMPLEX

Techniques of freeze-fracturing and cytoplasmic maceration were combin ed to reveal the septal pore cap in some members of the Rhizoctonia s. l. complex by the use of field emission gun-scanning electron microsco py. Perforate septal pore caps were observed in Rhizoctonia solani, Aq uathanatephorus pendulus, Ceratobasidium cornigerum, and Waitea circin ata, showing a successive decrease in cap size. W. circinata revealed an irregular distribution of holes in the cap. Imperforate septal pore caps were observed in Epulorhiza anaticula and Sebacina vermifera. Th e cap of E. anaticula was connected to tubular endoplasmic reticulum, while the cap of S. vermifera was connected to platelike endoplasmic r eticulum. Scanning microscopy is a useful method to complement our kno wledge of the septal pore cap as it shows the septal pore cap in situ in relation with other organelles. Septal pore caps present within the Rhizoctonia s.l. complex can be subdivided into: (i) a perforate sept al pore cap with either regularly or irregularly distributed holes; (i i) an imperforate septal pore cap connected with tubular endoplasmic r eticulum or with platelike endoplasmic reticulum. Our results sustain the current classification of the investigated species in four orders.