Biological control of phytopathogens by phloroglucinol and hydrolytic enzyme producing bacterial inoculants

Envionmental and consumer concerns have focused interest on the development of biological control as an alternative, environmentally-friendly strategy for the protection of agricultural and horticultural crops against phytopathogens. Biological control agents. producing a variety of secondary metabolites and hydrolytic enzymes, have been identified among fungi, actinomyceles and bacteria. Pseudomonas fluorescens FII3 and Stenotrophomonas maltophilia W81 inhibit growth of the phytopathogenic fungus Pythium ultimum in vitro and are capable of protecting sugar beet against the effects of damping-off under soil conditions. Transposon mutagenesis of strains FIl3 and W81 has demonstrated that the biocontrol abilities of these strains are mediated by 2,4-diacetylphloroglucinol (pm...) or lytic enzyme production, respectively. Globodera roslochiensis is a phytopathogenic cyst neml1.tode of major agronomic importance. Purified PHL, lytic enzymes, and chitinolytic or phloroglucinol-producing bacterial inoculants negatively influence hatch of G. rostochiensis eggs and decrease subsequent viability of juvenile cyst nematodes in vitro. Similar results were obtained under soil conditions.