Submitted to: Proceedings of Workshop on Global Int Org Biocontrol (IOBC) Working Group
Publication Type: Proceedings
Publication Acceptance Date: 9/20/2005
Publication Date: 2/20/2006
Citation: Mavrodi, D., Validov, S., Mavrodi, O., De La Fuente, L., Weller, D.M., Thomashow, L.S. 2006. Antagonistic activity among 2,4-diacetylphloroglucinol (dapg)-producing fluorescent pseudomonas spp.. Proceedings of Workshop on Global Int Org Biocontrol (IOBC) Working Group. Vol. 29(2), pg 97-100. Interpretive Summary: Take-all is one of the most important root diseases of wheat world wide. Take-all decline (TAD) is a natural biocontrol of take-all that develops when wheat is grown in monoculture. In Washington State, TAD results from the build-up of strains of Pseudomonas fluorescens that produce the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) in the rhizosphere of wheat. This research demonstrates that the ability to produce bacteriocins is a common trait among 2,4-DAPG producers an may contribute to their ability to colonize wheat roots.
Technical Abstract: Certain strains of Pseudomonas fluorescens that produce the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) can colonize roots and suppress soilborne pathogens more effectively than other strains that otherwise are almost identical. We recovered DNA fragments from the superior root colonizer P. fluorescens Q8r1-96 by suppression subtractive hybridization with the moderate colonizer strain Q2-87 in order to identify genetic differences that might account for superior colonization activity. One clone from Q2-87 exhibited similarity to a pore-forming bacteriocin and resides in a 23-kb pyocin-like gene cluster that includes a functional two-gene lysis module and a bacteriophage tail assembly. Treatment of strain Q8r1-96 with mitomycin C caused production of phage tail-like particles. Subsequent screening to in vitro revealed that bacteriocin activity was common among 2,4-DAPG-producing isolates representing 17 distinct genotypes. Such activity may contribute to strain competitiveness and persistence in vitro and in the rhizosphere.