Biosurfactants are involved in the biological control ofVerticilliummicrosclerotia byPseudomonasspp.

Abstract

Aims: To examine the effect of previously described bacterial antagonists on the viability of Verticillium microsclerotia in vitro and to elucidate the possible modes of action of bacterial strains in the suppression of Verticillium microsclerotia viability. Methods and Results: A microplate assay was developed to test the suppressive effect of well‐defined Pseudomonas spp. on the viability of Verticillium microsclerotia in vitro. Experiments using phenazine‐ and biosurfactant‐deficient mutants indicated that biosurfactants and phenazine‐1‐carboxylic acid play a role in the suppression of microsclerotia viability by Pseudomonas spp. In addition, microsclerotia colonization tests revealed that Pseudomonas spp. are able to colonize the surface of the microsclerotia, but not the inner matrix. Growth response curves showed that the population levels of Pseudomonas spp. increased when they were in the vicinity of Verticillium microsclerotia, indicating that Pseudomonas spp. may utilize nutrients from the microsclerotia for their growth. Conclusions: Pseudomonas spp. seem to be good candidates for Verticilllium microsclerotia biocontrol. Biosurfactant production is one of the main mechanisms involved in their mode of action. Significance and Impact of the Study: This line of work may contribute to a better understanding of biological control agents and their working mechanisms.

Temperature-Dependent Expression of phzM and Its Regulatory Genes lasI and ptsP in Rhizosphere Isolate Pseudomonas sp. Strain M18

“…It is known that PCA and PYO are the two important varieties of phenazines produced in various pseudomonads, although the relative quantities and functional roles of PCA and PYO produced in pseudomonads were not strictly distinguished and carefully studied in many publications. PCA and PYO were considered to have similar physiological and biochemical functions in cells (13); however, the different functional roles of PCA and PYO have been described in a few publications recently (10,16,28,57). Based on the methods used in this study, it would be quite difficult to compare our PCA and PYO measurements with those in other studies, where PCA was mainly assayed at pH 4.0 by UV spectroscopy of high-performance liquid chromatography at 248 nm, while PYO was assayed at pH 7.0 by measuring OD 520 (9,14,45,58,59).…”

Jasmonate signaling in plant interactions with resistance-inducing beneficial microbes

“…They can stimulate plant growth by enhancing the plant's photosynthetic capacity (Zhang et al, 2008), by increasing tolerance to abiotic stress (Yang et al, 2009), or by suppressing plant diseases (Harman et al, 2004;Kloepper et al, 2004;Pozo and Azcon-Aguilar, 2007;Van Loon et al, 1998) and insect herbivory (Van Oosten et al, 2008;Zehnder et al, 2001). The disease suppressive activity of PGPR and PGPF is exerted either directly by hampering growth and development of soil-borne pathogens through competition for nutrients or secretion of antibiotics in the rhizosphere (Bakker et al, 2007;De Bruijn et al, 2007;Debode et al, 2007;Handelsman and Stabb, 1996;Kamilova et al, 2008), or indirectly by eliciting a plant-mediated systemic resistance response (Kloepper et al, 2004;Van Loon et al, 1998;Van Wees et al, 2008). Systemic resistance triggered by beneficial microorganisms confers a broad-spectrum resistance that is effective against different types attackers.…”

Isolation and functional analysis of the pathogenicity-related gene VdPR3 from Verticillium dahliae on cotton

“…4a, 5a). Consistent with these observations, microsclerotia of V. dahliae have always been considered important targets for Verticillium disease control (Debode et al 2007). Furthermore, VdPR3 deletion mutants were only weakly invasive with low dispersive ability in cotton, and less stem discoloration was observed in cotton plants inoculated with ΔVdPR3 (Fig.…”