Control of Verticillium dahliae by adding olive mill waste to the rhizosphere of nursery grown plants

Plant-growth substrates containing stabilized residues from different biomass are being studied as alternative plant growth substrates not only for their agronomic properties, but also for their suppressiveness against phytopathogens. In this study two matrices containing olive mill wastes, obtained by advanced processes (composting or aerobic static storage), were tested for their suppressive effect against Verticillium wilt (Verticillium dahliae). In growth chamber and nursery trials, these innovative substrates were mixed at 15% (v/v) with a standard growing matrix for young olive plants, artificially contaminated with V. dahliae microsclerotia (MS). The dynamic of V. dahliae MS in the growth mixtures was periodically monitored by selective media as well as by real-time PCR. The assayed matrices interfered with disease development by significantly reducing both V. dahliae MS density in the rhizosphere and plant mortality.