CORDIER, CHRISTELLE1, NURIA FERROL1, JOSE-MIGUEL BAREA1, SILVIO GIANINAZZI2 & VIVIENNEGIANINAZZI-PEARSON2.
1Estación Experimental del Zaidín, CSIC, 18008 Granada, SPAIN. 2Laboratoire de Phytoparasitologie INRA/CNRS, CMSE-INRA, BV 1540,21034 Dijon cédex, FRANCE.
The ability of arbuscular mycorrhiza to decrease root disease caused by soil borne pathogens is well recognized, but very little is known about the mechanisms that are really active. We have analysed interactions between Glomus mosseae and Phytophthora parasitica in roots of Lycopersicum esculentum in order to elucidate tissue, cellular and molecular phenomena underlying bioprotection. Using a split root experimental system, we have shown that the control of P. parasitica in mycorrhizal tomato root systems involves induction of a localized resistance in arbuscule-containing cells and a systemic resistance in non mycorrhizal tissues.Ultrastructural investigations coupled with histochemical and immunocytochemical analyses have provided evidence that decreased pathogen development in both mycorrhizal and non mycorrhizal parts of mycorrhizal root systems is associated with the elicitation of host wall modifications, together with the accumulation of defence-related molecules. Present investigations are aimed at characterizing plant genes expressed during bioprotection of mycorrhizal tomato challenged with P. parasitica.
Key words: biocontrol - induced resistance -cytomolecular analyses - wall modifications - defence molecules.