COLONIZATION AND PATHOGEN INHIBITION ANALYSIS OF BIOLOGICAL CONTROL RHIZOBACTERIA PRODUCING ANTIFUNGAL COMPOUNDS

THE SUCCESSFUL APPLICATION OF BIOLOGICAL CONTROL AGENTS TO FIELD DISEASE CONTROL PROBLEMS IS LIMITED TO A FEW RESTRICTED EXAMPLES. ONE BASIC LIMITATION IN OUR KNOWLEDGE OF THE MECHANISMS OF BIOLOGICAL CONTROL WITH RHIZOSPHERE COLONIZING BACTERIA (RHIZOBACTERIA) HAS BEEN THE LACK OF RIGOROUS TESTING OF THE ROLE OF ANTIBIOTICS PRODUCED DURING COLONIZATION. IN THIS RESEARCH, WE PROPOSE TO EVALUATE THE ROLE OF DIFFERENT ANTIFUNGAL COMPOUNDS PRODUCED BY TWO PSEUDOMONAS FLUORESCENS RHIZOBACTERIA IN THE CONTROL OF COTTON SEEDLING DISEASE CAUSED BY PYTHIUM ULTIMUM AND RHIZOCTONIA SOLANI. THE STRAINS TO BE USED IN THESE TESTS WERE DERIVED BY SITE-DIRECTED MARKER EXCHANGE TO CREATE MUTANTS PARENTAL STRAINS. THE RHIZOSPHERE COMPETENCE, COLONIZATION POTENTIAL AND DISEASE PROTECTION WILL BE TESTEDIN A MODEL SOIL SYSTEM IN WHICH THE PARENTAL STRAINS HAVE BEEN SHOWN TO GIVE SIGNIFICANT BIOLOGICAL CONTROL OF P. ULTIMUM. BETTER UNDERSTANDING OF THE MECHANISMS OF DISEASE PROTECTION AND RHIZOSPHERE COMPETENCE IS ESSENTIAL TO BROADEN THE SUCCESSFUL USE OF THESE BIOLOGICAL CONTROL AGENTS AS A COMMERCIAL SEED TREATMENT.