Induced suppressiveness to Fusarium oxysporum f.sp radicis lycopersici in rockwool substrate used in closed soilless systems

Tomatoes grown in soilless systems can be seriously damaged by Fusarium oxysporum Schlect f.sp. radicis lycopersici (Forl) causing Fusarium crown and root rot (FCRR). FCRR suppression can be achieved through the use of chemicals, selected substrates, composts and artificially introduced antagonistic microorganisms. This study evaluated the natural capacity of a used rockwool to suppress FCRR infections. New and used rockwool, sampled from closed soilless systems, was either autoclaved or not, either artificially inoculated with Forl or not and, finally, sown with tomato seeds cv. 'Cuore di Bue'. The effects of autoclaved/non-autoclaved and used/new rockwool on FCRR incidence were assessed by evaluating the symptoms of crown rot on the root - shoot transition zone of tomato seedlings. Non-autoclaved and inoculated used rockwool significantly reduced FCRR incidence when compared with non-autoclaved and inoculated new rockwool. Autoclaved and inoculated used rockwool did not suppress FCRR, similarly to new and inoculated rockwool. These findings are in accordance with other research that, on a cucumber/Pythium host/pathogen complex in a closed rockwool soilless system, demonstrated the key role of resident microflora in suppressing the root rot disease.