The effects of triclosan on spore germination and hyphal growth of the arbuscular mycorrhizal fungus Glomus intraradices.

The effect of triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol; TCS), on spore germination, hyphal growth, and hyphal branching of the arbuscular mycorrhizal (AM) fungus, Glomus intraradices spores was evaluated at exposure concentrations of 0.4 and 4.0 μg/L in a static renewal exposure system. To determine if potential effects were mycotoxic or a consequence of impaired signaling between a host plant and the fungal symbiont, spores were incubated with and without the addition of a root exudate. Exposed spores were harvested at days 7, 14, and 21. AM spore germination, hyphal growth, and hyphal branching were significantly lower in both TCS concentrations compared to controls in non-root exudate treatments suggesting direct mycotoxic effects of TCS on AM development. Greater hyphal growth and hyphal branching in controls and 0.4μg/L TCS treatments with root exudate compared to non-root exudate treatments demonstrated growth stimulation by signaling chemicals present in the root exudate. This stimulatory effect was absent in the 4.0 μg/L TCS treatments indicating a direct effect on plant signaling compounds or plant signal response.