Suppressiveness to Fusarium oxysporum f. sp. radicis lycopersici in re-used perlite and perlite–peat substrates in soilless tomatoes

This work reports the occurrence of suppressiveness to Fusarium oxysporum f. sp. radicis lycopersici (FORL) on recycled perlite and perlite–peat mix from closed and open soilless systems. Nine soilless systems were sampled from three different sites in Northern and Southern Italy and different parameters, including sampling site, growing period before sampling, electric conductivity of the nutrient solution, tomato cultivar, and irrigation system were considered. The effects on seed germination and FORL incidence on tomato seedlings were finally assessed with or without additional artificial inoculation of the pathogen and with or without autoclaving the samples prior to inoculation. Suppression of FORL was experimentally evaluated with a technique already adopted for rockwool. Results collected on perlite and perlite–peat confirmed the possibility to reduce FORL severity on recycled substrates. Only the composition of the substrate (perlite, perlite–peat mix) and the disinfestation did affect the incidence of FORL. Suppression of FORL was observed in not disinfected recycled perlite–peat substrates while a reduction of FORL incidence was also been recorded in disinfected and recycled perlite. Disease incidence decreased from an average ranging from 44.4% to 61.9% in new perlite to 2.5–36.3% in recycled one. Similarly disease incidence decreased from an average ranging from 35.9% to 75.2% in new perlite–peat mix to 0.4–26.4% in recycled perlite–peat mix. In conclusion the recorded data suggest the possibility to consider FORL suppression as a predictable phenomenon when recycled substrates (perlite, perlite–peat mix) are adopted.