Abstract: Two commercial biological products Proradix®Agro (Pseudomonas sp.) and Salavida(P. trivialis) were assayed on young tomato plants under Phytophthora infestans challenge, undergreenhouse conditions. The products were water suspended following producer’s instruction andapplied to the soil 6 days before the foliar inoculation with P. infestans. Late blight symptomswere observed 4 days after pathogen inoculation. Untreated plants appeared more infected thantreated plants, but no statistically significant difference was found between treatments andcontrols or between the two products. However the application of each product led to a visibleplant growth enhancement. A comparative study was carried out in order to highlight proteomedifferences among treated/untreated and inoculated/non inoculated plants. Total proteins wereextracted from leaves collected 48h after pathogen inoculation and analysed by two-dimensionalelectrophoresis. The bioproduct application followed by the pathogen inoculation led toup/down-regulation of some protein spots which were different from those affected by thepathogen only. Mass-spectrometry analysis will be carried out in order to clarify if the observedmodifications concern the activation of defence mechanisms or the observed plant growthpromotion.