Pseudomonas fluorescens mediated antifungal activity against Rhizoctonia solani causing sheath blight in rice [Oryza sativa L. - India]

Antifungal activity of Pseudomonas fluorescens strains PF, FP7 and PB2 was tested against the rice sheath blight pathogen Rhizoctonia solani. The bacterial strains produced antibiotic 2,4-diacetyl phloroglucinol, iron chelating siderophore, hydrogen cyanide, lytic enzymes, such as chitinase and beta...

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Published in:Phytopathologia mediterranea 2002-08, Vol.41 (2), p.109-119
Main Authors: Nandakumar, R, Babu, S, Radjacommare, R, Raguchander, T, Samyappan, R. (Tamil Nadu Agricultural Univ., Coimbatore (India). Dept. of Plant Pathology)
Format: Article
Language:English
Subjects:
ANTIBIOTICI
ANTIBIOTICS
ANTIBIOTIQUE
ANTIBIÓTICOS
BIOLOGICAL CONTROL
CHITINASE
CHITINASI
CONTROL BIOLÓGICO
CONTROLLO BIOLOGICO
ENFERMEDADES FUNGOSAS
FUNGAL DISEASES
INDE
INDIA
LUTTE BIOLOGIQUE
MALADIE FONGIQUE
MALATTIE FUNGINE
ORYZA SATIVA
PSEUDOMONAS FLUORESCENS
QUITINASA
RESEARCH PAPERS
RHIZOCTONIA SOLANI
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Summary:Antifungal activity of Pseudomonas fluorescens strains PF, FP7 and PB2 was tested against the rice sheath blight pathogen Rhizoctonia solani. The bacterial strains produced antibiotic 2,4-diacetyl phloroglucinol, iron chelating siderophore, hydrogen cyanide, lytic enzymes, such as chitinase and beta-1,3-glucanase in culture and induced chitinase in plants. Soaking R. solani sclerotia in either bacteria-free culture filtrates or in sap extracted from plants treated with Pseudomonas strains PF1 and FP7 or inoculated with R. solani significantly reduced the germination capacity of the sclerotia. The inability of treated sclerotia to cause sheath blight symptoms indicated loss of virulence. In all the experiments, strain PF1 or FP7 always performed better than PB2. The 35 kDa chitinase induced by Pseudomonas in rice plants was purified and its antifungal activity against mycelium and sclerotia of R. solani was demonstrated. The production of antibiotics, antifungal compounds, bacterial lytic enzymes and the induction of plant chitinase were correlated with antifungal activity against R. solani sclerotia [E' stata saggiata l'attivita' antifungina di Pseudomonas fluorescens ceppi PF, FP7 e PB2 nei confronti di Rhizoctonia solani, agente della rizottoniosi della guaina del riso. I ceppi batterici producevano l'antibiotico 2,4-diacetil floroglucinolo, sideroforo chelante il ferro, acido cianidrico, enzimi litici, come chitinasi e beta-1,3-glucanasi in coltura e induceva la chitinasi nelle piante. L'infiltrazione degli sclerozi di R. solani con filtrati di coltura esenti da batteri o con linfa estratta da piante trattate con i ceppi di Pseudomonas PF1 e FP7 o inoculate con R. solani ne riduceva significativamente la capacita' di germinazione. L'incapacita' degli sclerozi trattati di causare i sintomi della malattia dimostrava una perdita di virulenza. In tutti gli esperimenti, il ceppo PF1 o il ceppo PF7 si comportavano sempre meglio rispetto a PB2. La chitinasi di 35 kDa indotta da Pseudomonas nelle piante di riso e' stata purificata ed e' stata dimostrata la sua attivita' antifungina nei confronti del micelio e degli sclerozi di R. solani. La produzione di antibiotici, composti antifungini, enzimi litici batterici e l'induzione della chitinasi nelle piante e' state correlata con l'attivita' antifungina nei confronti degli sclerozi di R. solani]
ISSN:0031-9465
1593-2095