Protozoa stimulate the plant beneficial activity of rhizospheric pseudomonads

SIMONE WEIDNER; ELLEN LATZ; BETINA AGARAS; CLAUDIO VALVERDE; ALEXANDRE JOUSSET

PLANT AND SOIL

SPRINGER

Lugar: Berlin; Año: 2017 vol. 410 p. 509 - 515

0032-079X

Background and AimsThe functioning of plant-associated bacteria is strongly influenced by their interactionwith other organisms. For instance, bacteria upregulate the production of secondarymetabolites in presence of protozoa and we hypothesised that this interaction maycontribute to plant health.MethodsHere, we tested if the effect of beneficial pseudomonads on plant growth and health ismodified by co-inoculation with the bacterivorous amoeba Acanthamoeba castellanii.We assessed promotion of wheat growth in absence and decrease of growth inhibitionin presence of the root pathogen Pythium ultimum.ResultsIn absence of amoebae, isolates had few beneficial effects with some exacerbatinggrowth inhibition by the pathogen (despite their reported in vitro effects). Effects on plant growth in absence and presence of the pathogen were negatively correlated.Co-inoculation with amoebae suppressed this relationship, leading to plant growthpromotion in absence and reduction of deleterious effects in presence of the pathogen.The effect of amoebae in absence of the pathogen could be related to bacterialsiderophore production in vitro.ConclusionsOur results illustrate the discrepancy between in vitro and in vivo effects of plantbeneficial bacteria. Incorporation of other rhizospheric trophic components such asprotists may be a key factor to influence the plant-beneficial potential of bacteria invivo.