Analogous wheat root rhizosphere microbial successions in field and greenhouse trials in the presence of biocontrol agents Paenibacillus peoriae SP9 and Streptomyces fulvissimus FU14

Authors: ARAUJO, RICARDO - Flinders University; Dunlap, Christopher; FRANCO, CHRISTOPHER - Flinders University

Submitted to: Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2020
Publication Date: 2/14/2020
Citation: Araujo, R., Dunlap, C., Franco, C.M.M. 2020. Analogous wheat root rhizosphere microbial successions in field and greenhouse trials in the presence of biocontrol agents Paenibacillus peoriae SP9 and Streptomyces fulvissimus FU14. Molecular Plant Pathology. 21(5):622-635. https://doi.org/10.1111/mpp.12918.
DOI: https://doi.org/10.1111/mpp.12918

Interpretive Summary: ARS researchers from Peoria, IL collaborated with scientists from Flinders University to understand how treating wheat with microbial biocontrol agents alter the microbes inside the roots. The biocontrol agents had limited impact on the microbes inside the roots of wheat. The biocontrol agents were also determined to persist in the root environment for approximately 8 weeks after inoculation. The research shows wheat seedlings undergo a dramatic shift in root microbes during the first few months of growth. This study will allow us to better understand the mode of action of these beneficial microbes. This research benefits U.S. farmers and consumers that rely on wheat.

Technical Abstract: The wheat microbiome is highly dynamic but the impact on endophytic and rhizosphere communities has rarely been studied in plants treated with endophytic biocontrol inoculants. These treatments promote plant growth and confer protection against fungal root diseases, hence monitoring co-occurrence of taxa is relevant for ecological balance and community dynamics. In the present study, we detail the microbiome dynamics of the endo- and ecto-rhizosphere (for both bacteria and fungi) associated with the initial stages of a wheat cropping system in the field and concurrently in the glasshouse. The system allowed the following hypotheses to be tested: (1) the root microbiome is defined by microbial successions; (2) there are specific differences between the endophytes observed in field and glasshouse trials; (3) the addition of biocontrol agents can be detected during the early stages of plant growth; and (4) neither the biocontrol organisms nor the pathogenic agents have major effects on the root and rhizosphere microbiomes. Bacteria played a stronger role in early stages of wheat growth, while fungi gained prominence in the root and rhizosphere microbiomes after 12 week of wheat crop cycle. Some bacterial and fungal genera were succeeded from early to late stages, being added to enrich the plant microbiome. It was possible to track several bacteria and fungi to the initial source, seed versus rhizosphere soil. Roots obtained from Streptomyces-coated seeds accounted for lower Shannon diversity when compared with the other roots at similar stage. Biocontrol added agents were consistently found in the wheat roots up to 8 weeks. The addition of biocontrol agents to wheat as seed coats has generally low impact on microbial communities and its safety was confirmed for soil ecosystems. Lewia, Sordaria and Mortierellaceae were significantly affected when comparing field and glasshouse trials. This study provides detailed information on the key microorganisms (bacteria and fungi) that associate with wheat roots at different stages of growth.