Tomato production in Spanish intensive systems is increasingly employing the potting culture with organic substrates. Verticillium dahliae is a possible phytopathogen of this culture. The aim of this study was to evaluate composted cork Verticillium wilt of tomato suppressiveness. A bioassay was carried out using tomato var. Marmande and two isolates of V. dahliae (307 and Tor 600). Light peat was used as a reference. Substrates were infested at densities of 0, 104 and 105 conidia ml~(-1) substrate.Disease severity was recorded 25 days after transplantation on a scale based on the percentage of symptomatic leaves, according to which 0 = symptomless, 1 < 50%, 2 ≥ 50% and 3 = 100%. The main chemical properties, microbial activity, biomass and carbonmetabolic profiles (Biolog~(R)) of peat and composted cork were compared. Composted cork infested with isolate 307 showed a disease severity significantly lower than that of peat at both pathogen densities tested. However, composted cork infested with Tor 600 showed a disease severity significantly lower than that of peat only when infested at 104 conidia ml~(-1). At the end of the bioassay, both substrates had the same pH but not the same elements availability. High calcium availability was associatedwith lower Verticillium wilt incidence, whereas low potassium availability correlated with higher disease incidence. The suppressive composted cork showed lower calcium and potassium availability than peat, suggesting that potassium and calcium do not play a major role in this system. The biological properties of the substrates also differed significantly. In composted cork, both microbial activity and biomass were higher than in peat. In addition, peat and composted cork microbiota carbon metabolic profiles also differed significantly. These results indicate that biological characteristics may play a major role on Verticillium wilt suppression.
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