Cultured parsley cells, a model system for the rapid testing of abiotic and natural substances as inducers of systemic acquired resistance

Abstract

In cultured parsley (Petroselinum crispumL.) cells, chemical and natural agents that are known to induce systemic acquired resistance (SAR) in different plant species were checked for their ability to condition the cells for an enhanced response to low doses of an elicitor from the cell wall of the fungal pathogenPhytophthora sojae. Use of the fluorescence properties of elicitor-induced furanocoumarin phytoalexins in the culture fluids of parsley cells allows rapid testing of many substances over a broad range of concentrations for their SAR-inducing capacity. Except for probenazole, a number of agents which have been described as effective inducers of disease resistance in plants were able to activate cells for an enhanced elicitor-mediated furanocoumarin accumulation. Among the compounds tested, benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester, the active ingredient of the commercially available SAR activator Bion®, was found to have the highest potential for conditioning parsley cells. On the other hand, compounds which are known to be inactive as inducers of disease resistance failed to enhance the elicitor response. The results suggest that cultured parsley cells provide a suitable system for the identification of SAR-inducing agents.Using the parsley test system, the artificial sweetener saccharin, a substance not previously reported to induce SAR in plants, was found to be very effective in conditioning the cells for an enhanced accumulation of coumarin derivatives. Furthermore, when applied to cucumber, tobacco and bean plants, saccharin was found to induce resistance against both fungal and viral diseases.