AN ULTRASTRUCTURAL-STUDY OF THE INTERACTION BETWEEN SPONGOSPORA-SUBTERRANEA F-SP NASTURTII AND WATERCRESS ROOTS

The early stages (up to 72 h) of the infection cycle of Spongospora su bterranea f. sp. nasturlii were investigated. Within 48 h, zoospores e ncysted an roots and produced adhesoria, the cyst wall which formed du ring zoospore encystment underwent changes in morphology. Cysts contai ned a dense-staining bullet-like stachel which may be involved in host penetration, this was contained within a long striated tube, the rohr . By 72 h, intracellular uninucleate myxamoebae were observed which ap parently engulfed host cell contents with pseudopodia to form ingestio n vacuoles. Cell to cell movement of myxamoebae, by host wall penetrat ion, appeared to be mediated by enzymic degradation.