LOW-TEMPERATURE TECHNIQUES AS A TOOL IN PLANT PATHOLOGY

In plant pathology, low temperature preparation techniques now appear to be feasible methods to stabilize the dynamic ultrastructure of the host-(plant)-pathogen (fungi) interaction for an analysis by transmiss ion electron microscopy. A well defined ultrastructure of small organi sms (fungi) and large biological samples such as plant material and as well as the plant-pathogen (fungus) infection sites are presented. Th e mesophyll tissue of Arabidopsis thaliana is characterized by homogen eously structured cytoplasm closely attached to the cell wall. Infecti on sites of stem rust (Puccinia graminis f. sp. tritici) on primary le aves of wheat (Triticum aestivum) and powdery mildew (Erysiphe gramini s f.sp. hordei) on coleoptiles of barley (Hordeum vulgare) are analyze d with regard to the fine structural preservation of the haustoria, th e extrahaustorial matrix and the extra-haustorial membrane. Recent dat a on the immunocytochemical characterization of freeze substituted rus t and powdery mildew infected plant tissue are described with special emphasis on the localization of elicitor glycoproteins involved in the cellular host-parasite interaction. There is clear evidence for the r elease of the elicitor glycoprotein into the extrahaustorial matrix of the haustorial complex. No elicitor molecules are seen in the plant h ost cytoplasm.