Mycoparasitism of potato black scurf pathogen (Rhizoctonia solani Kuhn) by biological control agents to sustain production

Eight isolates of Trichoderma harzianum and six isolates of Pseudomonas fluorescens were tested in vitro for their antagonistic potential against Rhizoctonia solani. In dual culture both bioagents were found antagonistic to the growth of R. solani. The hyphal interaction studied using light microscopy revealed destructive mycoparasitism of R. solani by T. harzianum mycelium. The method of mycoparasitism was sparse to intense coiling of R. solani followed by disintegration, disorganization and death of R. solani mycelium. Similarly, addition of bacterial antagonist P. fluorescens inhibited the growth of R. solani by disintegrating mycelium even without contact of two colonies. When sclerotia of R. solani, parasitized by the antagonist T. harzianum and P. fluorescens were studied under microscope, the outer cells of sclerotia showed disintegrated breakdown of cell wall and extrusion of cytoplasm. Since, conidiophores and conidia of T. harzianum were also observed in sections of parasitized sclerotia, an active parasitization of sclerotia by antagonist is indicated. Sclerotia of R. solani was completely destroyed by bioagents within 25 days of interaction under laboratory conditions.