Fluorescent Pseudomonads in the Phyllosphere of Wheat: Potential Antagonists Against Fungal Phytopathogens

Abstract

Fluorescent pseudomonads isolated from wheat leaves were characterized regarding their antagonistic potential and taxonomy in relation to protect crop plants from infestation by Fusarium and Alternaria fungi causing diseases in wheat. Using a dual culture assay, inhibition of fungal growth was found for 40 isolates of 175 fluorescent pseudomonads. Twenty-two of the antagonists were able to suppress strains of Fusarium as well as Alternaria. By means of real-time qPCR, the phlD gene encoding the antibiotic 2,4-diacetylphloroglucinol was detected in 20 isolates. On the basis of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry spectral patterns, the isolates with antagonistic activity were assigned to the phylogenetic subgroup Pseudomonas fluorescens and the closely related Pseudomonas gessardii subgroup. The results of the study suggest that pseudomonads in the phyllosphere of crop plants may possibly contribute to natural plant protection.

Spotlight on the Underdogs—An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

“…Interactions of fungi and bacteria with Alternaria could exist more often in competition and in antagonistic processes than in undisturbed coexistence. Few studies dealing with the co-occurrence of Fusarium and fluorescent pseudomonads with Alternaria suggest the implication of mycotoxins as antagonistic substances in these interactions [52,53] Simultaneously, competition processes between different fungal genera affect the production of mycotoxins or increase the metabolization of toxins [54,55]. That means that the production of mycotoxins in natural habitats is influenced by biotic and abiotic factors and could represent various toxin profiles and different concentrations of mycotoxins [56,57].…”

The distribution of mycotoxins in a heterogeneous wheat field in relation to microclimate, fungal and bacterial abundance

“…Starting from Fusarium mycotoxins, Müller et al . (, 2016a, 2016b) observed similar concentrations for DON and ZEN (also abbreviated as ZEA) in years with a similar rainfall in June. DON.3G showed also concentrations comparable to previous studies (Berthiller et al .…”

“…In contrast, mycotoxins did not show any clear correlation with microclimatic variables, except DON which showed a weak positive correlation with soil humidity at the second sampling date and harvest, similar to those reported by Müller et al . (2016a, 2016b).…”

“…Pseudomonas fluorescens includes a wide variety of strains, showing different behaviours (Müller et al . 2016a, 2016b; Yoshida et al . ).…”

“…An antagonistic activity towards Fusarium was shown with isolates from the phyllosphere (Müller et al . 2016b) and in studies targeting the rhizosphere (Henkes et al . ; Dudenhöffer et al .…”