Chemicobiological Insight into Anti-phytopathogenic Properties of Rhizospheric Serratia plymuthica R51

Interest in biocontrol of plant pathogens has increased in recent years due to agricultural trend towards greater sustainability and public concern over the use of hazardous pesticides. In the present study, rhizobacteria isolated from Curcuma amada were screened for their antifungal activity against phytopathogens. Among these, the isolate R51 was found to have promising activity against selected phytopathogens in dual culture. The antifungal compound containing fraction was purified by column chromatography and was identified by ultra violet spectrum (UV), infra-red spectrum (FT-IR) and mass spectroscopic (LC–MS) analyses as pyrrolnitrin. By scanning electron microscopic (SEM) analysis, the isolate R51 was found to cause vacuolation, swelling, distortion and lysis of mycelia of the pathogenic fungi. R51 was identified as Serratia plymuthica and was found to provide effective protection to ginger rhizome from soft-rot caused by Pythium myriotylum. Hence, the chemicobiological basis of antifungal activity of Serratia plymuthica can be due to pyrrolnitrin [3-chloro-4-(2′-nitro-3′-chlorophenyl) pyrrole] production and is having significant agricultural applications.