Inhibitory Activity of Pseudomonas putida and Bacillus licheniformis Supernatants on PMMoV in Chili Pepper

Background and objective: Plant viruses are major obstacles to enhancing crop productivity in both agriculture and horticulture throughout the world, resulting in losses of several billion dollars every year. Controlling viruses is arduous, so agrochemicals are widespread. To minimize the usage of those, this study's objective was to assess bacterial cultures supernatants on pepper mild mottle virus (PMMoV) in chili pepper plants and identify its secondary metabolites. Methods: This 48-h grown Pseudomonas putida (PP) and Bacillus licheniformis (BL) cultures supernatants were foliar sprayed separately in chili pepper plants 24-h before PMMoV inoculation (T1), and 24-h before and after PMMoV inoculation (T2), 2wpi (week's post inoculation), the virus titer was determined by using a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), and the supernatants were extracted with ethyl acetate and concentrated by rota-evaporation before being analyzed in gas chromatography mass spectrometry (GC-MS). Results: The culture supernatants of PP and BL inhibit PMMoV by 43-47% in both the treatments (T1 & T2) compared to the control. The GC-MS chromatogram of two cultures of supernatants identified the molecules of cyclo (Pro-Val), cyclo (Pro-Leu), and cyclo (Phe-Pro). Commercial forms of these three molecules at three concentrations showed a hypersensitive response, ranging from 45-65% for PMMoV in Nicotiana glutinosa. Conclusion: The results revealed that supernatants of PP and BL-containing compounds have biological control of PMMoV in chili pepper plants.