In vitro and in vivo nematicidal activity of prodigiosin against the plant-parasitic nematode Nacobbus celatus

Among the natural antagonistic microorganisms of plant-parasitic nematodes are rhizobacteria of the genus Serratia. Some species can produce a red pigment known as prodigiosin, which has shown to be antagonistic to different organisms. We analysed the nematicidal potential of this metabolite obtained from a Serratia marcescens strain on the nematode, Nacobbus celatus. In the first experiment, mortality of second-stage juveniles (J2) from two Argentine populations (Río Cuarto and Santa María from Córdoba and Catamarca provinces, respectively) was estimated at different concentrations of the metabolite at 24 and 48 h in vitro. Based on the percentages obtained, lethal doses 50 (LD50) and 90 (LD90) were determined. LD50 for Río Cuarto and Santa María was 12.4 and 13.2 μg/mL, respectively, whereas LD90 was 24.9 μg/mL for both populations. In the second experiment, both LDs were applied in the soil and at 12 days after inoculation, J2 that had penetrated tomato roots were counted. The application of prodigiosin to the soil reduced nematode root invasion by 59% (LD50) and 83% (LD90) with respect to control. Our in vivo results also evidence the efficacy of the compound in the soil at very low concentrations. The pigment reveals, for the first time, to be an alternative method for biological control of N. celatus.