A non-pathogenic strain of Fusarium oxysporum and grape marc compost control Verticillium wilt of olive

Verticillium wilt of olive (VWO), caused by the widespread soil-borne fungus Verticillium dahliae Kleb., is currently the most serious disease affecting olive trees (Olea europaea L.) in all production areas. An integrated management strategy using eco-friendly approaches such as genetic resistance and biological control is considered the most advisable approach for controlling the disease in commercial olive orchards. This study evaluated a non-pathogenic strain of F. oxysporum (FO12) and the grape marc compost CGR03 for reducing inoculum density of V. dahliae and the disease progress in two olive cultivars with different VWO resistance levels. The experiment was conducted under semi-controlled conditions, using a naturally infested soil with two inoculum densities of V. dahliae. The biocontrol treatments (FO12 and CGR03) were previously selected out of 220 natural products as two of the most effective treatments against the pathogen. FO12 and CGR03 treatments significantly reduced pathogen inoculum density in comparison with that of the control (P = 0.05), with minimum microsclerotium amounts of 0.13 g-1 for FO12 and 0.53 g-1 for CGR03, during the experimental period. CGR03 reduced the progression of the disease compared with that in the control (P = 0.05), and FO12 achieved complete control of VWO, since no plants treated with this biological control strain developed VWO symptoms. This study highlights the effectiveness of these biocontrol treatments, and the potential use of eco-friendly approaches for control of VWO.