# Growth promotion and stress tolerance of soybean plants driven by seed treatment with synthetic bacterial community of soybean-associated beneficial bacteria

## TL;DR

This study shows that treating soybean seeds with a synthetic bacterial community can boost plant growth and resilience to stress and disease.

## Contribution

The novel contribution is the development of synthetic bacterial communities that enhance soybean growth and stress tolerance through microbiome restructuring.

## Key findings

- Two synthetic bacterial community sets (Set2 and Setm4) significantly improved soybean growth and resistance to Rhizoctonia solani.
- Seed treatment with these communities increased soybean resilience to drought and waterlogging.
- SBC application enriched symbiotic taxa like Bradyrhizobium elkanii and increased microbial network complexity in soybean roots.

## Abstract

Beneficial microbes provide a sustainable approach to improving crop production and reducing risks from intensive farming. Microbial consortia, complementary traits, often outperform single strains in promoting plant health. This study aimed to develop an effective biological strategy to enhance soybean growth and health using beneficial bacterial consortia.

Bacteria were isolated from the root endosphere and rhizosphere of field-grown soybean plants and screened for traits such as nutrient solubilization, hormone production, and pathogen suppression. Seven synthetic bacterial communities (SBCs), each comprising 5 to 20 SABB strains, were constructed to evaluate their potential in promoting soybean growth and health. Impact of SBC seed treatments on the structure of soybean microbiota was also investigated.

Two SBC sets, Set2 and Setm4, demonstrated superior performances in enhancing plant growth and resistance to the fungal pathogen Rhizoctonia solani when applied via seed treatment. Notably, seed treatment with Set2 or Setm4 also improved soybean resilience to abiotic stresses, including drought and waterlogging. Profiling of the root endosphere and rhizosphere microbiota revealed that SBC application through seed treatment significantly altered the composition of soybean-associated microbial community, including the enrichment of key symbiotic taxa, such as Bradyrhizobium elkanii, and increased microbial network complexity.

The beneficial effects of SBC through seed treatment are closely related to microbiome restructuring in soybean roots. This study provides valuable insights into the development of innovative and sustainable crop management strategies, highlighting the potential of SBC-based seed treatments to enhance growth and stress resilience in soybeans and other major crops.