# First report of a novel Paenibacillus strain JDF1 and its biocontrol potential against citrus bacterial canker

## TL;DR

A new Paenibacillus strain, JDF1, was found to effectively control citrus bacterial canker without harming plants and is stable at high temperatures.

## Contribution

The discovery of a novel Paenibacillus strain with strong biocontrol potential against citrus bacterial canker.

## Key findings

- JDF1 inhibited Xcc in vitro and eliminated citrus canker symptoms in greenhouse trials without phytotoxicity.
- JDF1 retained over 60% activity after heat treatment at 50°C for 6 hours, showing thermostability.
- Genome analysis revealed JDF1 produces multiple antibiotics, including bacilysocin, contributing to its biocontrol potential.

## Abstract

Citrus bacterial canker (CBC), caused by Xanthomonas citri subsp. citri (Xcc), causes severe annual yield losses on citrus crops worldwide. Current control strategies including quarantine, copper-based chemicals, and resistant varieties are limited by poor adaptability, pathogen resistance, and long breeding cycles. Herein, a novel endophytic Paenibacillus strain, designated JDF1, was isolated from Veronica persica (a common weed in citrus orchards). In vitro assays demonstrated that JDF1 inhibited Xcc. Greenhouse trials with “Eureka” lemon showed that low-concentration JDF1 (OD600 = 0.2) and its cell-free supernatant eliminated CBC symptoms without inducing phytotoxicity. Notably, JDF1 retained over 60% of its activity following heat treatment at 50 °C for 6 h. Phylogenetic analyses revealed that JDF1 is closely related to P. xylanexedens (98.52% 16S rRNA gene similarity) and P. polysaccharolyticus (99.8% housekeeping gene similarity). Further average nucleotide identity (ANI) analysis confirmed that strain JDF1 belongs to the same species as P. polysaccharolyticus, with a sequence similarity of 97.31%. JDF1 tolerated CaCuSO4 concentrations up to 600 mg/L and exhibited resistance to ampicillin and streptomycin. Genome sequencing of JDF1 predicted multiple genes associated with antibiotic biosynthesis, primarily including those involved in the production of polyketide, terpenoid, tyrocidin A, iturin A, lanthipeptide (class II), ranthipeptide, and lassopeptide. In a deeper investigation of the biocontrol mechanisms, a phospholipid antibiotic, bacilysocin, was identified in the JDF1 culture via LC-MS analysis. Collectively, these findings indicate that JDF1 is a promising novel biocontrol agent (BCA) against Xcc, with the dual advantages of high efficacy at low concentrations and thermostability, thereby enhancing its potential for agricultural application.