The ultrastructure of Endothia parasitica. Comparison of a virulent with a hypovirulent isolate

Hyphae of virulent (v) Endothia parasitica isolate 16-15-1 (West Virginia) and hypovirulent (hv) isolate Ep-4 (France) were preserved by freeze-substitution, embedded, and longitudinally sectioned to describe and compare their subcellular structure. General ultrastructural features of both were similar. Apical vesicles and uncoated microvesicles were common constituents of the extreme hyphal apex. Abundant membranous material also was seen in this region in some tip sections of hv isolate Ep-4. Filasomes were located along the lateral hyphal wall just behind the apex, and one was observed to be fused with the plasmalemma. Golgi cisternae were numerous in the tip area and appeared very flat and fenestrated, and often were closely associated with mitochondria. Components of the vacuole system were variously shaped, totally electron dense in young hyphae, and lighter with discernible inclusions in older hyphae. Spherical, membrane-bounded viruslike particles (VLPs), 51–78 nm in diameter, were observed in tip...