Silicon Suppresses Fusarium Crown and Root Rot of Tomato

Fusarium oxysporum f.sp. radicis‐lycopersici , the causal agent of Fusarium crown and root rot (FCRR), is a serious soilborne disease of tomato. Soil fumigation and host resistance may reduce the impact of this disease, but other alternative management strategies are needed because these options may not always be available or effective. The purpose of this study was to determine the potential of silicon (Si) to reduce the disease severity of FCRR. Seven‐day‐old seedlings of Bonny Best tomato, susceptible to FCRR, were transplanted in sand culture amended with Hoagland’s nutrient solution with (+Si) or without (−Si) 100 mg Si/l. At 3 weeks after transplanting, three inoculum concentrations 0, 10 6 and 10 7 conidia/plant were used to inoculate the seedlings. Disease severity and silicon concentration were evaluated at 4 weeks after inoculation. Disease progress over time was investigated using the seedlings amended with Si or without Si and inoculated with 0 or 10 6 conidia/plant. Disease severity was evaluated at 2, 3, 4 and 6 weeks after inoculation. After rating disease, evaluated plants were divided into shoots and roots for silicon concentration analysis. Si significantly reduced the severity of FCRR on the stem of tomato at 4 weeks after inoculation. Results of disease progress suggested that the decrease in the disease severity of FCRR by Si amendment was probably due to a delay in onset in initial infection of roots and the movement of the pathogen from roots to stems. Si contents of roots and shoots were significantly higher in tomato plants supplied with Si than in those without Si. Moreover, the increase in the Si content of roots was significantly correlated with the reduction of disease severity of root, crown and stem, indicating a silicon‐mediated resistance. Supplying Si to tomato seedlings can reduce the disease severity of FCRR, providing an alternative disease management strategy.