Mentha and Oregano Soil Amendment Induces Enhancement of Tomato Tolerance against Soilborne Diseases, Yield and Quality

Tomato is considered among the most important horticulture crops in both temperate and tropical regions, and two of the major biotic stresses include Fusarium oxysporun f.sp. lycopersici (Fol) and Verticillium dahliae (Vd). The effect of soil incorporated spearmint and oregano dried plant material on physiological, yield and quality parameters of tomato, along with their efficacy against soilborne fungal diseases, was studied in pot experiments conducted in a greenhouse environment. Tomato plants grown in soil amended with spearmint or oregano showed better agronomical characteristics (taller plants with thicker stems) and improved physiological ones (higher chlorophyll content index and photosynthetic rate). Yield was increased and the qualitative features of tomato fruits were enhanced. In addition, plants grown in soil amended with spearmint or oregano and inoculated with Fol or Vd had no visual disease symptoms 50 days from the inoculated tomato transplantation, except from plants grown in soil amended with oregano and inoculated with Fol, which showed symptoms of chlorosis and leaves loss. These enhancements on physiological parameters and on disease suppression resulted in increased fruit yields of plants–grown in soil amended with spearmint and oregano and inoculated with Fol or Vd–by 77%–95% compared with free-disease controls. GC-MS analysis of volatiles derived from soils amended of either spearmint or oregano indicated that several constituents remained in the soil environment long after incorporation of plant material, although, at lower concentrations and considerable modified. The current study reveals that direct incorporation of spearmint or oregano plant material into the soil could improve tomato tolerance against soilborne fungi, soil fertility and consequently increase yield and product quality.