A 'paper bridge' system to improve in-vitro propagation of arbuscular mycorrhizal fungi

The in-vitro culture of arbuscular mycorrhizal fungi on excised roots, especially when performed on bicompartmented Petri dishes, has proven to be an efficient system for the production of root-free fungal material. However, even after the contact between fungal hyphae and the excised roots in the proximal root compartment has occurred, up to several weeks may be required for the fungal runner hyphae to cross the median Petri dish wall and reach the distal fungal compartment. This delay is particularly long for the cultivation of slow-growing strains that usually colonize the substrate less aggressively. The delay is due to the difficulty the runner hyphae have in crossing the median Petri dish wall that separates compartments. To facilitate the passage of the fungus across the median wall, a 'paper bridge' system has been devised and tested with a number of arbuscular mycorrhizal fungal strains. This method substantially accelerated fungal propagation and simplified the manipulations necessary. The proposed paper-bridge system is described and its advantages discussed. Key words: arbuscular mycorrhizal fungi. Glomus, paper bridge, in-vitro culture. La culture in vitro des champignons mycorhiziens arbusculaires sur racines excisees, notamment en boites de Petri bi-compartintentees, constitue un systeme efficace de production axenique de champignon. Bien que le contact hyphe-racines s'effectue rapidement dans le compartiment racine, plusieurs semaines peuvent etre requises par les hyphes pour traverser dans la partie distale du systeme. Ce delai, particulierement long pour les souches a croissance lente et peu agressives, est du principalement a la difficulte pour les hyphes de traverser la cloison centrale qui separe les compartiments. Afin de remedier a celle difficulte un >> poni de papier << teste sur une diversite de souches myeorhiziennes s'est avere efficace pour accelerer la propagation fongique tout en simplifiant substantiellement les manipulations. Le systeme est decrit et ses avantages discutes. Mots-cles: champignons mycorhiziens arbusculaires. Glomus, pont papier, culture in vitro.
Introduction Since 1975, when Hepper and Mosse first established cultures of arbuscular mycorrhizae (AM) on excised roots, tremendous improvements have been made with the use of Ri T-DNA transformed roots [...]