ENDOPHYTES OF WILD ORCHIDS NATIVE TO ITALY: THEIR MORPHOLOGY, CARYOLOGY, ULTRASTRUCTURE AND CYTOCHEMICAL CHARACTERIZATION

Isolates of Rhizoctonia sp. obtained from the terrestrial orchids Dactylorhiza sambucina (L.) Soó, D. maculata (L.) Soó and Platanthera bifolia (L.) L. C. M. Richard, collected in Piedmont (Italy) were studied in the following characters: macroscopic and microscopic morphology, growth rate, ultrastructure of the septal pore apparatus, number of nuclei per cell and cytochemistry of the hyphal and monilioid cells. On the basis of cultural and morphometric characters, the isolates were divided into three groups, which are described in detail. No perfect stage was produced in culture. Although the identification of species of Rhizoctonia‐like fungi without perfect stages is extremely difficult, a comparison of our data with that in the literature leads to the probable identification of group I isolates as a species of Ceratobasidium, group II isolates as a species of Thanatephorus and those of group III as a species of Tulasnella or Sebacina.