AN ELECTRON-MICROSCOPIC STUDY OF THE INFECTION OF THE NEMATODE PANAGRELLUS-REDIVIVUS BY THE ENDOPARASITIC FUNGUS VERTICILLIUM-BALANOIDES

The infection of nematodes by the endoparasitic fungus Verticillium ba lanoides was studied by means of optical and electron microscopical te chniques. Conidia of this fungus adhere randomly in high numbers to th e entire cuticle surface of the nematode Panagrellus redivivus. Adhesi on is accomplished by means of a tri-layered adhesive pad located at t he apical end of the conidium, the outermost layer of which shows a ra diated substructure. After attachment an appressorium which grows thro ugh the adhesive pad and establishes a firm contact between the fungal cell wall and the nematode cuticle is formed. Penetration of the cuti cle by means of a hyphal outgrowth on the appressorium is followed by the formation of an infection bulb from which trophic hyphae develop t hat invade the nematode. Approximately 60 h after infection conidiopho res develop outside the nematode, producing numerous conidia.