Bacteriophages Targeting an Emerging Pantoea spp. for Rice Disease Biocontrol

Bacterial plant diseases caused by the genus Pantoea have emerged as severe threats to global rice cultivation, causing destructive conditions such as bacterial leaf blight and grain rot. Due to increasing antibiotic resistance and the environmental hazards of chemical pesticides, bacteriophage-based biocontrol offers a promising, eco-friendly alternative. In this study, we isolated and characterized novel bacteriophages from infected rice paddies in Thailand, using a newly identified host, Pantoea sp. isolate 2 based on 16S rRNA gene sequencing. Transmission electron microscopy revealed that the phages belong to the class Caudoviricetes: phage vB_PS-10 displays a siphovirus-like morphotype, whereas phage vB_LX1 exhibits a myovirus-like morphotype. One-step growth analysis of vB_PS-10 uncovered a biphasic propagation pattern with a latent period of 30 min and a burst size of 10 PFU/cell. In vitro lytic assays demonstrated that vB_PS-10 significantly suppressed bacterial growth, achieving a 4 log CFU/mL reduction in host cells after 12 h. Stability assays revealed that vB_PS-10 is highly stable across a broad pH range (6.0–10.0) and resilient at tropical field temperatures (35–45 °C), though sensitive to UV-C radiation and direct sunlight. Finally, a detached leaf assay validated its in planta biocontrol efficacy, showing that phage vB_PS-10 exhibited a significant reduction in disease severity, restricting lesion development to just 13.8% ± 4.37%, whereas the pathogen-only control group showed near-total lesion coverage after 7 days. These findings demonstrate that phage vB_PS-10 has robust potential as a sustainable biological control agent to manage emerging Pantoea diseases in rice production.