Antibiosis-mediated necrotrophic effect of Pseudomonas GRC(2) against two fungal plant pathogens

A fluorescent Pseudomonas GRC(2) isolated from rhizosphere of potato, showe d necrotrophic antibiosis in vitro against two major plant pathogens, Macro phomina phaseolina and Sclerotinia sclerotior um. After 5 days of incubatio n at 28 +/- 1 degreesC, this strain caused clear inhibition zones in dual c ulture, restricting the growth of M phaseolina and S. sclerotiorum by 80.1% and 73.5%, respectively. Scanning electron photomicrographs from the zone of interaction showed loss of sclerotial integrity, hyphal shrivelling, myc elial and sclerotial deformities and hyphal lysis in M. phaseolina. Hyphal perforations, lysis and fragmentation were observed in case of S. sclerotio rum. Similar result was also observed when both the pathogens were grown on tryptic soy agar medium juxtaposed to 5-day-old culture filtrate of Pseudo monas GRC(2). These morphological abnormalities in fungal pathogens were du e to production of antifungal secondary metabolites by Pseudomonas GRC(2).