EFFECT OF Pseudomonas fluorescens ON GROWTH OF MEDICINAL PLANTS AND ITS BIOCONTROL EEFECT ON SELECTED PHYTOPATHOGENS

Abstract

Pseudomonas fluorescens is Plant Growth Promoting Rhizobacteria that aggressively colonize the root zone and promote plant growth are generally termed as Plant Growth Promoting Rhizobacteria (PGPR). P. fluorescens act as biocontrol agents as well as plant growth promoter as it produce different types of secondary metabolites likes iron chelating siderophores, hydrogen cynide, exoenzymes, phytohermones, antibiotic and helps to adopts the plants from various stressed conditions. They also protect plants from phytopathogens by controlling or inhibating them, improves soil structure, bioremediates that pollutes soil by sequestering toxic heavy metal species and degrading xenobiotic compounds like pesticides. The aim of study is to isolate and identify P. fluorescens from rhizospheric soil of Dhankuta, Sunsari, Morang, Jhapa and Illam to observe its effects on growth of medicinal plants and its biocontrol effect on some phytopathogens. The rhizospheric soil was collected from 5 districts of eastern Nepal, in sterile plastic bag and cultured in king’s B media by serial dilution and incubated at 25°C for 48 hrs. Morphological, cultural, biochemical and physiological characterization was done and bacteria were identified. Isolated P. fluorescens were cultured on Kings B broth and inoculated on medicinal plants by deep root technique. In vitro effects on selected phytopathogens were observed on Modified Kings B media by dual culture method. It was found that marigold and mint inoculated with P. fluorescens was so healthy with increase in height, no. of branches, fresh and dry weight. Increament in height of marigold and mint was found to be around 31% and 28.9% comparing to that of uninoculated plants. Similarly, different isolates were found to suppress different plant pathogens being the D1 most potent in suppressing S. rolfsii, JF and DR being most potent in suppressing R. solani and Alternaria spp respectively. While other isolates were found to moderate potent.