Does drought stress modify the effects of plant‐growth promoting rhizobacteria on an aboveground chewing herbivore?

Abstract

Soil microbes have important effects on the interactions of plants with their environment, by promoting plant growth, inducing resistance to pests or by conferring tolerance to abiotic stress. However, their effects are variable and the factors responsible for this variation are mainly unknown. Our aim was to assess how drought stress modifies the effect of the nonpathogenic rhizobacterium Pseudomonas simiae WCS417r on plant growth and resistance against the generalist leaf-chewing caterpillar Mamestra brassicae. We studied Arabidopsis thaliana Col-0 plants, as well as mutants altered in the biosynthesis of the phytohormones jasmonic acid (JA) and abscisic acid (ABA). Caterpillars did not prefer rhizobacteria-treated plants, independently of drought stress. Rhizobacteria colonization had a variable effect on caterpillar performance, which ranged from positive in one experiment to neutral in a second one. Drought had a consistent negative effect on herbivore performance; however, it did not modify the effect of rhizobacteria on herbivore performance. The effect of drought on herbivore performance was JA-mediated (confirmed with the use of the dde2-2 mutant), but it was still present in the ABA-deficient mutant aba2-1. Plant biomass was reduced by both drought and herbivory but it was enhanced by rhizobacterial colonization. Pseudomonas simiae WCS417r is able to promote plant growth even when plants are suffering herbivory. Nevertheless, the microbial effect on the herbivore is variable, independently of drought stress. To get the best possible outcome from the rhizobacteria-plant mutualism it is important to understand which other factors may be responsible for its context-dependency.

The Role of Plant-Associated Microbes in Mediating Host-Plant Selection by Insect Herbivores

“…Most studies of microbe-plant-herbivore interactions to date have focused on tripartite interactions within controlled environmental conditions. A few exceptions include studies that have considered abiotic factors like soil nutrients [169] or drought stress [170]. There is abundant evidence that abiotic factors, such as water or nutrient availability [171], solar radiation [172], and temperature [173] influence plant physiology and defensive traits.…”

Denkkader licht : Naar een effectief gebruik van LED belichting in de glastuinbouw

“…Sterker nog, abiotische stressfactoren, zoals UV-straling en droogte, kunnen de afweer van het gewas tegen ziekten en plagen vaak juist verhogen (Demkura and Ballare 2012, Kruidhof et al 2012, Mewis et al 2012, de Bobadilla et al 2017, Escobar-Bravo et al 2017.…”

The promises and challenges of research on plant–insect–microbe interactions

“…Fernandez de Bobadilla et al . () tested whether drought stress modulates the impact of a PGPR on resistance to a chewing herbivore. Interestingly, they showed that whereas drought itself had a strongly negative impact on herbivore performance, it did not alter the effect of PGPR on herbivore resistance.…”

“…This has triggered an increased interest in how the (a)biotic environment modulates the effects of root symbionts on plant-herbivore interactions. Fernandez de Bobadilla et al (2017) tested whether drought stress modulates the impact of a PGPR on resistance to a chewing herbivore. Interestingly, they showed that whereas drought itself had a strongly negative impact on herbivore performance, it did not alter the effect of PGPR on herbivore resistance.…”

“…One of the obstacles for using plant-associated beneficial microbes to enhance pest control is the low predictability of their effects under varying environmental or cultivation conditions (Razinger et al, 2017). A major challenge is therefore to understand the abiotic factors governing such context-dependency and its underlying mechanisms (de Bobadilla et al, 2017;Karley et al, 2017). Another important challenge is that in the real world these beneficial microbes function in a whole (rhizosphere/phyllosphere) community (i.e., phytobiome), urging a shift toward studies that can shed light on how the effectiveness of these microbes in enhancing pest resistance is modulated in a community context (Lachaise et al, 2017).…”