Phenylpropanoids Produced by Piper divaricatum, A Resistant Species to Infection by Fusarium solani f. sp. piperis, the Pathogenic Agent of Fusariosis in Black Pepper

In a previous study, the essential oil (EO) of Piper divaricatum showed strong antifungal activity in vitro against Fusarium solani F. sp. piperis. For this reason, the seedlings of P. divaricatum were inoculated with the pathogen to evaluate the in-vivo resistance. Evaluation of symptoms and analysis of secondary metabolite production from infected and non-infected plants occurred at 7, 21, 30 and 45 days post inoculation (dpi). Throughout the experiment, the infected seedlings did not display symptoms of infection or significant variation of total phenolic compounds. However, lipoxygenase (LOX) enzymatic activity, which is involved in the defense mechanism, had increased in the 21 and 45 dpi. In addition, the EOs were analyzed by GC-MS. The EOs from infected plants showed a substantial increase in the concentrations of phenylpropanoid compounds, particularly on days 21 and 45 dpi. The main constituent was methyl eugenol, which reached 95.3% in the infected sample at 45 dpi, followed by eugenol acetate with a variation of 6.1% to 10.7%, between 21 and 30 dpi. These results suggest an incompatible plant-pathogen interaction and involvement of various volatile compounds from P. divaricatum in the resistance mechanism.