Submitted to: Mycological Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/3/2007
Publication Date: 2/7/2007
Citation: Nagahashi, G., Douds, D.D. 2007. Separated components of carrot root exudates are specifically exuded and stimulate two different types of hyphal branching responses of an arbuscular mycorrhizal fungus. Mycological Research. 111:487-492. Interpretive Summary: Arbuscular mycorrhizal fungi are soil borne and are capable of infecting most crop plants. They are beneficial to the host plant by supplying nutrients in the soil, which the roots can’t extract by themselves, and thereby increase crop growth and yield. The fungus receives sugar molecules from the host which are absolutely required for its survival. The production of fungal spores, which could be used to inoculate agricultural fields, could reduce or supplant the use of chemical fertilizers and their water pollution problems. To provide a useful inoculum, it is necessary to identify the factors which allow the germinated spores to find a host plant in the soil. We have discovered the presence of two compounds, which are made by the host plant and diffuse into the soil, that are capable of stimulating the growth and branching of the fungus. Both of these factors give the fungus a greater chance to contact a host root in the soil. This knowledge and practical use of this knowledge can be used to increase the successful fungal colonization of a host plant thereby providing an efficient way to apply this “biofertilizer”.
Technical Abstract: Components found specifically in the exudates of carrot roots and not found in the cytoplasm, were separated by thin layer chromatography (TLC). Six bands, which stimulated hyphal branching of the arbuscular mycorrhizal fungus Gigaspora gigantea, were initially separated by single dimension TLC. The separated bands were then further separated by two-dimensional TLC. Five of the separated components stimulated the typical branching morphology reported for AM fungi grown in vitro in culture. One band of activity generated a different type of branching response compared to the other five components. This compound diffused faster, stimulated more lateral branching for a longer period of time, and generated different morphology in branching pattern compared to other branching stimulators.