INSTYTUT DENDROLOGII

Ultrastructural and cytochemical aspects of the mycoparasitic activity of mycorrhizal fungus Laccaria laccata

The morphological and cytological aspects of mycoparasitic activity of mycorrhizal fungus Laccaria laccata against expansive soil saprobes Trichoderma harzianum, T. virens and Mucor hiemalis were studied in in vitro. This study provides information which is crucial to our understanding of how these interactions occur in the soil environment. Using scanning electron microscopy this study revealed that short and ramified branches of L. laccata captured and coiled around the spores and hyphae of saprotrophic fungi. This was confirmed with transmission electron microscope. The changes in the cell walls compounds labeling and the presence of phenolics at the point of contact of the interacting fungi were shown. Furthermore, the release of an adhesive material to external spaces at the point of contact between hyphae of L. laccata and structures of saprobes was observed. This suggests that the mycorrhizal fungus can parasitize saprotrophic fungi not only in co-culture on artificial medium but also in the rhizosphere of Scots pine. In a related study the morphology of the microtubular cytoskeleton and mitochondria during mutual interaction in co-culture of Laccaria laccata with Trichoderma harzianum and T. virens was also examined. In hyphae growing within the interaction zone, microtubules became wavy and eventually fragmented or depolymerised, and mitochondria also became fragmented which suggests that the studied fungi antagonistically affect each other at a cellular level. Finally, the ability of mycorrhizal fungi to transfer phosphorus ³²P from spores of saprotrophic fungi and subsequent translocation it to the plant during ectomycorrhizal symbiosis was studied. It was revealed that the ectomycorrhizal fungi: L. laccata and Suillus bovinus, mobilized the phosphorus from radioactive conidia of saprotrophic fungi. On this basis it is concluded that activities of the mycosymbionts may facilitate absorption and further translocation of phosphorus from organic matter into the host-plants.