Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2008
Publication Date: 3/29/2008
Citation: Okubara, P.A., Bonsall, R.F. 2008. Accumulation of pseudomonas-derived 2,4-diacetylphloroglucinol on wheat seedling roots is influenced by host cultivar-bacterial strain interaction. Biological Control. 46(2008)322-331.
Interpretive Summary: This study reports the use of a soil-free Petri plate system to grow wheat roots after inoculation with biocontrol isolates of the bacterium Pseudomonas fluorescens, which suppresses root pathogens, partly by production of the antifungal metabolite 2,4-diacetylphloroglucinol (2,4-DAPG). We used this system to explore the relationship between root colonization, host cultivar, bacterial isolate, and 2,4-DAPG accumulation on wheat roots. After four days, P. fluorescens Q8r1-96, an aggressive root colonizer, produced significantly more 2,4-DAPG than Q2-87 (a less aggressive colonizer) on the roots of two wheat cultivars. However, both bacterial isolates produced similar levels of the metabolite on a third host. Populations of the bacteria on the roots were at maximum levels in all treatments, indicating that the differences in metabolite accumulation were not due to amounts of colonizing bacteria. To our knowledge, this is the first report of cultivar-dependent 2,4-DAPG accumulation on roots of wheat. Our findings have implications for the interplay between host and bacterial factors that regulate 2,4-DAPG levels in the rhizosphere.
Technical Abstract: Disease suppression of soilborne pathogens by fluorescent pseudomonads (rhizobacteria) is a sustainable means of controlling root diseases, but the efficacy of rhizobacteria is subject to host and environmental factors. As part of a broad study to determine how host factors impact rhizosphere persistence of biocontrol pseudomonads, we quantified steady-state levels of 2,4-DAPG produced by two isolates of