Abstract
BACKGROUND: Rice blast, caused by Pyricularia oryzae, is a devastating fungal disease threatening global rice production. Overreliance on chemical fungicides has raised environmental concerns and led to resistant strains, necessitating the development of sustainable alternatives. This study integrated marine microbiology and natural antifungal compounds to create eco-friendly alternatives to chemical fungicides for disease management. RESULTS: We identified Pseudomonas aeruginosa R64 with broad-spectrum antimicrobial activity from mangrove soil in the Mai Po Nature Reserve. The R64 fermentation extract (RFE) exhibited multifaceted inhibition of P. oryzae, suppressing mycelial growth, conidiation, conidial germination and appressorial formation, while disturbing cell wall and membrane function. It also attenuated virulence by impairing appressorial penetration and invasive growth. Further chemical analysis identified phenazines and quinolines as the primary compounds in RFE, corroborated by PCR detection of corresponding phenazine biosynthetic gene clusters. Comparative bioassays with two main bioactive components of RFE, phenazine-1-carboxamide (PCN) and phenazine-1-carboxylic acid (PCA), against P. oryzae implicated PCN as the principal antifungal effector. RFE and PCN had higher efficacy than tricyclazole in P. oryzae growth inhibition, but were less effective than isoprothiolane. Furthermore, RFE and PCN displayed lower acute ecotoxicity to an environmental indicator organism than isoprothiolane, suggesting their potential as sustainable biopesticides for rice blast management. CONCLUSION: Natural products from mangrove soil bacterium P. aeruginosa R64 inhibited key developmental and infection processes of P. oryzae, effectively reducing rice blast development. The promising disease inhibition and low ecotoxicity of mangrove-associated bacteria highlight their untapped potential for innovative, eco-friendly fungicide mining for sustainable agriculture. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Claims 13
Claim · model-written summary
Pseudomonas aeruginosa R64 had broad antimicrobial activity.
- Taxon
- rice
Oryza sativat0 - Interactor
- Pseudomonas aeruginosa R64
Pseudomonas aeruginosae0biocontrol_agent - Outcome
- broad-spectrum antimicrobial activitye0
- Setting
- Mai Po Nature Reservee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We identified Pseudomonas aeruginosa R64 with broad-spectrum antimicrobial activity from mangrove soil in the Mai Po Nature Reserve”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
RFE suppressed P. oryzae mycelial growth, conidiation and conidial germination.
- Taxon
- riceOryza sativat0
- Treatment
- R64 fermentation extract (RFE)e0
- Interactor
- P. oryzaee0pathogen
- Outcome
- mycelial growth, conidiation, conidial germinatione0
- Direction
- suppressinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The R64 fermentation extract (RFE) exhibited multifaceted inhibition of P. oryzae, suppressing mycelial growth, conidiation, conidial germination and appressorial formation”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
RFE suppressed P. oryzae appressorial formation.
- Taxon
- riceOryza sativat0
- Treatment
- R64 fermentation extract (RFE)e0
- Interactor
- P. oryzaee0pathogen
- Outcome
- appressorial formatione0
- Direction
- suppressinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The R64 fermentation extract (RFE) exhibited multifaceted inhibition of P. oryzae, suppressing mycelial growth, conidiation, conidial germination and appressorial formation”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
RFE disturbed pathogen cell wall and membrane function.
- Taxon
- riceOryza sativat0
- Treatment
- R64 fermentation extract (RFE)e1
- Outcome
- cell wall and membrane functione0
- Direction
- disturbinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while disturbing cell wall and membrane function”
t0“rice blast”
t1“rice blast”
e1“The R64 fermentation extract (RFE) exhibited multifaceted inhibition of P. oryzae, suppressing mycelial growth, conidiation, conidial germination and appressorial formation”
Claim · model-written summary
RFE impaired pathogen appressorial penetration and invasive growth.
- Taxon
- riceOryza sativat0
- Treatment
- R64 fermentation extract (RFE)e1
- Outcome
- appressorial penetration and invasive growthe0
- Direction
- impairinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It also attenuated virulence by impairing appressorial penetration and invasive growth”
t0“rice blast”
t1“rice blast”
e1“The R64 fermentation extract (RFE) exhibited multifaceted inhibition of P. oryzae, suppressing mycelial growth, conidiation, conidial germination and appressorial formation”
Claim · model-written summary
Phenazines and quinolines were identified as primary compounds in RFE.
- Taxon
- riceOryza sativat0
- Outcome
- phenazines and quinolines as the primary compounds in RFEe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Further chemical analysis identified phenazines and quinolines as the primary compounds in RFE”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
Phenazine biosynthetic gene clusters were detected by PCR.
- Taxon
- riceOryza sativat0
- Gene
- phenazine biosynthetic gene clusterse0
- Outcome
- PCR detectione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“corroborated by PCR detection of corresponding phenazine biosynthetic gene clusters”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
Bioassays implicated PCN as the main antifungal component against P. oryzae.
- Taxon
- riceOryza sativat0
- Interactor
- P. oryzaee0pathogen
- Compound
- PCNe0
- Outcome
- principal antifungal effectore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Comparative bioassays with two main bioactive components of RFE, phenazine-1-carboxamide (PCN) and phenazine-1-carboxylic acid (PCA), against P. oryzae implicated PCN as the principal antifungal effector”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
RFE inhibited P. oryzae growth more than tricyclazole but less than isoprothiolane.
- Taxon
- riceOryza sativat0
- Treatment
- RFEe0
- Interactor
- P. oryzaee0pathogen
- Outcome
- P. oryzae growth inhibitione0
- Direction
- higher efficacye0
- Qualifier
- less effective than isoprothiolanee0
- Comparator
- tricyclazolee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RFE and PCN had higher efficacy than tricyclazole in P. oryzae growth inhibition, but were less effective than isoprothiolane”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
PCN inhibited P. oryzae growth more than tricyclazole but less than isoprothiolane.
- Taxon
- riceOryza sativat0
- Treatment
- PCNe0
- Interactor
- P. oryzaee0pathogen
- Outcome
- P. oryzae growth inhibitione0
- Direction
- higher efficacye0
- Qualifier
- less effective than isoprothiolanee0
- Comparator
- tricyclazolee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RFE and PCN had higher efficacy than tricyclazole in P. oryzae growth inhibition, but were less effective than isoprothiolane”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
RFE had lower acute ecotoxicity than isoprothiolane.
- Taxon
- riceOryza sativat0
- Treatment
- RFEe0
- Outcome
- acute ecotoxicity to an environmental indicator organisme0
- Direction
- lowere0
- Comparator
- isoprothiolanee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RFE and PCN displayed lower acute ecotoxicity to an environmental indicator organism than isoprothiolane”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
PCN had lower acute ecotoxicity than isoprothiolane.
- Taxon
- riceOryza sativat0
- Treatment
- PCNe0
- Outcome
- acute ecotoxicity to an environmental indicator organisme0
- Direction
- lowere0
- Comparator
- isoprothiolanee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RFE and PCN displayed lower acute ecotoxicity to an environmental indicator organism than isoprothiolane”
t0“rice blast”
t1“rice blast”
Claim · model-written summary
Bacterial natural products reduced rice blast development.
- Taxon
- riceOryza sativae0
- Treatment
- Natural products from mangrove soil bacterium P. aeruginosa R64e0
- Interactor
- P. oryzaee0pathogen
- Second interactor
- P. aeruginosa R64Pseudomonas aeruginosae0biocontrol_agent
- Outcome
- rice blast developmente0
- Direction
- reducinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Natural products from mangrove soil bacterium P. aeruginosa R64 inhibited key developmental and infection processes of P. oryzae, effectively reducing rice blast development”
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