# Antifungal Activity of Bacillus amyloliquefaciens X30 Against Botrytis fabiopsis 3-3 on Panax notoginseng and Its Mechanism

## TL;DR

A new strain of Bacillus amyloliquefaciens shows strong antifungal properties against a novel pathogen affecting Panax notoginseng, offering a potential eco-friendly solution for disease control.

## Contribution

Identification of Bacillus amyloliquefaciens X30 as a biocontrol agent with broad-spectrum antifungal activity and plant-growth-promoting traits.

## Key findings

- Strain X30 inhibited Botrytis fabiopsis 3-3 by 84.63% in vitro and showed broad antifungal activity against other pathogens.
- X30 produces antimicrobial compounds like phenylpyruvic acid and 2,6-dihydroxybenzoic acid with EC50 values of 312 and 660 µg/mL, respectively.
- X30 suspension achieved a 61.04% control rate in pot experiments against B. fabiopsis.

## Abstract

Gray mold disease severely impacts the yield and quality of Panax notoginseng (Burkill) F. H. Chen ex C. Chow & W.G. Huang. In this study, a strain of Botrytis fabiopsis J. Zhang, G.N. Wu & G.Q. Li labeled as 3-3 was isolated from the leaves affected by gray mould disease of P. notoginseng, identified as a novel pathogen for this plant. Targeting the strain 3-3, an antagonistic bacterial strain X30 was isolated from the leaves of P. notoginseng and was preliminarily identified as Bacillus amyloliquefaciens (Fukumoto) Priest et al. through morphological and molecular biological analyses. The in vitro antifungal test showed that strain X30, at a concentration of 1 × 108 CFU mL−1, had an inhibition rate of 84.63% against the B. fabiopsis strain 3-3, and it exhibited broad-spectrum antifungal activity against other major pathogenic fungi of P. notoginseng, including Alternaria alternata (Fr.) Keissl., Rhizoctonia solani J.G. Kühn and others. Additionally, strain X30 was found to produce ammonia, fix nitrogen, secrete plant growth hormones, and release multiple hydrolytic enzymes, thus possessing both plant-growth-promoting and antimicrobial traits. In pot experiments, an X30 suspension at 1 × 108 CFU mL−1 achieved 61.04% control rate against B. fabiopsis. Using non-targeted metabolomics, compounds in the culture filtrate of strain X30 were analyzed, and two organic acid compounds with antimicrobial activity were identified. Among them, phenylpyruvic acid had an EC50 value of 312 µg mL−1 against pathogen 3-3, while 2,6-dihydroxybenzoic acid had an EC50 value of 660 µg mL−1. B. amyloliquefaciens X30 provides a theoretical basis for developing green and efficient biocontrol agents against gray mould in P. notoginseng.