Phenazines and biosurfactants interact in the biological control of soil‐borne diseases caused by Pythium spp.

Abstract

In this study, the putative role of phenazines and rhamnolipid-biosurfactants, antagonistic metabolites produced by Pseudomonas aeruginosa PNA1, was tested in the biological control of Pythium splendens on bean (Phaseolus vulgaris L) and Pythium myriotylum on cocoyam (Xanthosoma sagittifolium L Schott). A rhamnolipid-deficient and a phenazine-deficient mutant of PNA1 were used either separately or jointly in plant experiments. When the mutants were applied separately, no disease-suppressive effect was observed, although both mutants still produced one of the antagonistic compounds (phenazines or rhamnolipids). When the mutants were concurrently introduced in the soil, the biocontrol activity was restored to wild-type levels. Bean seeds developed significantly less pre-emergence damping-off caused by P. splendens when treated with a mixture of purified phenazine-1-carboxamide and rhamnolipids than with any of the chemicals alone. When phenazines and rhamnolipids were combined at concentrations that had no observable effects when the metabolites were applied separately, mycelial growth of P. myriotylum was significantly reduced. In addition, microscopic analysis revealed substantial vacuolization and disintegration of Pythium hyphae after incubation in liquid medium amended with both metabolites. Results of this study indicate that phenazines and biosurfactants are acting synergistically in the control of Pythium spp.

Population Structure and Diversity of Phenazine-1-Carboxylic Acid Producing Fluorescent Pseudomonas spp. from Dryland Cereal Fields of Central Washington State (USA)

“…Since this discovery, many studies have shown that P. fluorescens 2-79 and other phenazine-producing (Phz + ) strains are effective biocontrol agents against common agriculturally significant soil-borne fungal pathogens (including Rhizoctonia, Fusarium, G. graminis var. tritici, and Pythium) when applied to seeds before planting [4,[6][7][8][9][10][11][12].…”

Antifungal activity of rhamnolipids against dimorphic fungi

“…They show potential applications in the biocontrol of Grampositive and Gram-negative bacteria, yeast, and fungi (Abalos et al, 2001;Kahraman and Erenler, 2012), and also insects as well (Kim et al, 2011). In particular, rhamnolipids can effectively control some plant pathogens such as Phytium aphanidermatum, Pythium splendens, Pythium myriotylum, Phythophthora capsici, Plasmopara lactucae-radicis and Colletotrichum orbiculare (Kim et al, 2000;Perneel et al, 2008;Stanghellini and Miller, 1997). Furthermore, they can induce plants to generate defense responses against fungal infections (Varnier et al, 2009).…”

Rhamnolipids Elicit Defense Responses and Induce Disease Resistance against Biotrophic, Hemibiotrophic, and Necrotrophic Pathogens That Require Different Signaling Pathways in Arabidopsis and Highlight a Central Role for Salicylic Acid

“…They have recently been shown to elicit plant defense responses and to induce resistance against B. cinerea in grapevine (Vitis vinifera; Varnier et al, 2009). They also participate to biocontrol activity of the plant beneficial bacteria Pseudomonas aeruginosa PNA1 against oomycetes (Perneel et al, 2008). However, the signaling pathways used by RLs to stimulate plant innate immunity are not known.…”