|YANG, MINGMING - Washington State University
|MAVRODI, DMITRI - University Of Southern Mississippi
|MAVRODI, OLGA - Washington State University
Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2017
Publication Date: 11/1/2017
Citation: Yang, M., Mavrodi, D.V., Mavrodi, O.V., Thomashow, L.S., Weller, D.M. 2017. Construction of a recombinant strain of Pseudomonas fluorescens producing both phenazine-1-carboxylic acid and cyclic lipopeptide for the biocontrol of take-all disease of wheat. European Journal of Plant Pathology. 149:683-694.
Interpretive Summary: Some biocontrol Pseudomonas bacteria produce cyclic lipopeptides (CLP), natural antibiotics that contribute to the ability of these bacteria to suppress soilborne plant pathogens that attack the roots of food, fiber and ornamental crops. However, these Pseudomonas biocontrol agents may show inconsistent performance to an important root disease of wheat known as take-all. In order to improve the biocontrol activity against take-all, we inserted into the CLP producer Pseudomonas strain HC1-07rif genes for the production of another natural antibiotic, phenazine-1-carboxylic acid (PCA). The recombinant strain Pseudomonas HC1-07PHZ inhibited the take-all pathogen better and controlled take-all at a lower dose as compared to the parent strain HC1-07rif. Thus, genetic engineering offers an approach to improve the ability of biocontrol agents to control plant diseases.
Technical Abstract: The primary mechanism of biocontrol by Pseudomonas fluorescens strains HC1-07 and HC9-07 is production of a cyclic lipopeptide (CLP) and phenazine-1-carboxylic acid, respectively. We introduced the seven-gene operon for the synthesis of phenazine-1-carboxylic acid (PCA) from P. synxantha 2-79 into Pseudomonas fluorescens HC1-07rif to determine if the biocontrol activity of the recombinant strain HC1-07PHZ increased against Gaeumannomyces graminis var. tritici, causal agent of take-all disease of wheat. In vitro inhibition assays showed that strain HC1-07PHZ consistently inhibited the hyphal growth of three isolates of the take-all pathogen on plates of both PDA and KMB, and the recombinant consistently inhibited G. graminis. var. tritici greater than the wild type. Strain HC1-07PHZ applied at a dose of 102 CFU seed-1 suppressed take-all better than strains HC1-07rif and HC9-07rif applied either individually or in combination. When the dose of the bacteria was increased to 104 CFU seed-1, the strain combination HC1-07rif + HC9-07rif showed significantly better disease suppression than did HC1-07rif, HC9-07rif or HC1-07PHZ applied individually. However, when the bacterial dose was increased to 107 CFU seed-1, strains HC1-07rif and HC1-07PHZ showed significantly better disease suppression than HC9-07rif and the combination HC1-07rif + HC9-07rif.