Shifts in the rhizobiome during consecutive in planta enrichment for phosphate‐solubilizing bacteria differentially affect maize P status

Abstract

Phosphorus (P) is despite its omnipresence in soils often unavailable for plants. Rhizobacteria able to solubilize P are therefore crucial to avoid P deficiency. Selection for phosphate-solubilizing bacteria (PSB) is frequently done in vitro; however, rhizosphere competence is herein overlooked. Therefore, we developed an in planta enrichment concept enabling simultaneous microbial selection for Psolubilization and rhizosphere competence. We used an ecologically relevant combination of iron-and aluminium phosphate to select for PSB in maize (Zea mays L.). In each consecutive enrichment, plant roots were inoculated with rhizobacterial suspensions from plants that had grown in substrate with insoluble P. To assess the plants' P statuses, nondestructive multispectral imaging was used for quantifying anthocyanins, a proxy for maize's P status. After the third consecutive enrichment, plants supplied with insoluble P and inoculated with rhizobacterial suspensions showed a P status similar to plants supplied with soluble P. A parallel metabarcoding approach uncovered that the improved P status in the third enrichment coincided with a shift in the rhizobiome towards bacteria with plant growthpromoting and P-solubilizing capacities. Finally, further consecutive enrichment led to a functional relapse hallmarked by plants with a low P status and a second shift in the rhizobiome at the level of Azospirillaceae and Rhizobiaceae.

Uncovering New Insights and Misconceptions on the Effectiveness of Phosphate Solubilizing Rhizobacteria in Plants: A Meta-Analysis

“…Recently, research has also turned to the non-destructive estimation of plant health and plant nutrient status. The use of multi- and hyperspectral imaging for the monitoring and estimation of a crop’s P-status is an uprising technique and could be used as a tool to better non-destructively assess the claim of P solubilization instead of plant growth promotion ( Gitelson et al, 2009 ; Rouphael et al, 2018 ; De Zutter et al, 2021 ).…”

“…This strategy might also result in loss of slow growing and/or unculturable bacteria with high rhizosphere competence and high P-solubilizing capacity. In this regard, implementing the rhizosphere competence as a trait in selection and enrichment strategies has shown promising results ( De Zutter et al, 2021 ).…”

Molecular Insights into Defense Responses of Vietnamese Maize Varieties to Fusarium verticillioides Isolates

“…The five germinated seeds were soaked in a fungal suspension (10 7 spores mL −1 ) for 1 h prior to transferal to five glass tubes containing mixed sand (200 g/tube) ( Figure S1 ). Five days before planting, 3 g polymer gel (DCM Aquaperla, Grobbendonk, Belgium) absorbed in 300 mL tap water was mixed with 2 kg non-sterile fine sand (Vosschemie Benelux, Lier, Belgium) [ 22 ]. Every two days, 10 mL of tap water was applied.…”

Streptomyces Strains Promote Plant Growth and Induce Resistance Against Fusarium verticillioides via Transient Regulation of Auxin Signaling and Archetypal Defense Pathways in Maize Plants

“…For the biocontrol treatment (FV + ST03 treatment), five germinated seeds were infected with F. verticillioides by soaking in a fungal suspension (10 7 conidia mL –1 ) for 1 h, and then sowed in five glass tubes (a seed per a tube) containing soil inoculated with the ST03 cell suspension. To inoculate the soil with Streptomyces , 3 g polymer gel (DCM Aquaperla, Grobbendonk, Belgium) absorbed in 300 mL tap water was mixed with 2 kg non-sterile fine sand (Voss chemie-Benelux, Lier, Belgium) ( De Zutter et al, 2021 ). This mixture was then inoculated with the ST03 cell suspension in a concentration of 10 6 CFU g –1 soil 3 days before planting.…”