# Investigating Bacillus amyloliquefaciens VFS2 for Vicia faba‐fusarium wilt biocontrol and plant growth promotion under osmotic stress

## TL;DR

This study explores how a bacteria called Bacillus amyloliquefaciens VFS2 can protect fava beans from fungal disease and help them grow better under drought and salt stress.

## Contribution

The study demonstrates that Bacillus amyloliquefaciens VFS2 is effective for biocontrol of Fusarium wilt in Vicia faba under osmotic stress conditions.

## Key findings

- Bacillus amyloliquefaciens VFS2 showed increased growth and antifungal activity under salt and drought conditions.
- The strain produced higher levels of plant growth-promoting substances like IAA and siderophores under osmotic stress.
- VFS2 effectively reduced Fusarium root-rot in fava beans under saline and drought conditions.

## Abstract

A dual assault from fungal infections and abiotic stress factors such as drought and salinity increasingly threatens fava bean production. These adverse conditions not only reduce crop yield and quality but also create a more conducive environment for fungal pathogens to thrive. In this study, we aim to investigate the potential of Bacillus amyloliquefaciens strain VFS2 for the biocontrol of Vicia faba‐Fusarium wilt under drought and salt stress.

The in vitro growth and sporulation of B. amyloliquefaciens VFS2 increased under salt and drought conditions (NaCl 0‐200 mM and PEG6000 0‐20%) in comparison to the unstressed control. The antifungal activity of VFS2 was screened against a broad‐spectrum of V. faba‐phytopathogenic fungi from the genera Fusarium, Boeremia, Rhizopus and Rutstroemia on PDA amended with NaCl (up to 200 mM) or PEG6000 (up to 20%), and the inhibition of fungal growth ranged from 50% to 98%. The ability of the VFS2 to produce various cLPs isoforms (iturins, fengycins, surfactins) under osmotic stress was demonstrated. The strain VFS2 also produces more IAA (up to 2.5 fold) and siderophores (up to 3 fold) under osmotic stress than in unstressed conditions. In biocontrol assays, VFS2 was effective in reducing V. faba root‐rot caused by F. equiseti VFF16 in saline soils (1.8 ≃ 1.9 ms m−1) and (up to 100%) under drought conditions (50% of water holding capacity).

Our findings indicate that B. amyloliquefaciens VFS2 has the ability to control Fusarium‐wilt and boost plant growth in extreme conditions. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The osmoadapted B. amyloliquefaciens VFS2 showed strong antifungal activities against Vicia faba‐pathogenic fungi and produced significant amounts of cLPs isoforms, indole‐3‐acetic acid, and siderophores under osmotic stress. These properties were associated with a Vicia faba Fusarium‐wilt disease biocontrol under saline and water‐deficient conditions. Consequently, B. amyloliquefaciens VFS2 is a promising biocontrol candidate of Fusarium‐wilt diseases amid the challenges of climate change.