Encapsulated eugenol from Pimenta racemosa var. racemosa as a biocontrol agent against Ralstonia solanacearum
摘要
Pimenta racemosa var. racemosa essential oil is effective in controlling the bacterial wilt of tomato caused by the Ralstonia solanacearum species complex. However, essential oils are not water-soluble and are easily degradable in the environment. Formulating the active ingredient could overcome these issues and improve the efficacy of the product. We aimed to test—in vitro and in vivo— the efficacy of Pimenta racemosa var. racemosa essential oil formulations and those of eugenol, its main component, against R. solanacearum. We characterized the clove chemotype of P. racemosa var. racemosa essential oil and then tested four formulations in vitro based on eugenol against R. solanacearum (Phylotype II/4NPB). We subsequently selected the most efficient formulation for in vivo tests in soil under semi-controlled conditions. The formulation containing CAPSUL® and 5% eugenol (Form2_eug) was the most efficient in vitro, and it significantly reduced the number and diameter of R. solanacearum colonies at all tested concentrations. In vivo, the same formulation applied to the soil as a diluted solution with a 0.3% eugenol concentration suppressed the R. solanacearum population. Under these semi-controlled conditions, the latter formulation was more efficient than the emulsified eugenol. Our results suggest that formulated eugenol, in encapsulated form, could be highly effective in controlling R. solanacearum. Following field validation, this formulation could be used as a biofumigant or a pre-planting soil treatment against bacterial wilt.