title: Role of salicylic acid in systemic resistance induced by Pseudomonas fluorescens against Fusarium oxysporum f. sp. ciceri in chickpea.
abstract: Selected isolates of Pseudomonas fluorescens (Pf1-94, Pf4-92, Pf12-94, Pf151-94 and Pf179-94) and chemical resistance inducers (salicylic acid, acetylsalicylic acid, DL-norvaline, indole-3-carbinol and lichenan) were examined for growth promotion and induced systemic resistance against Fusarium wilt of chickpea. A marked increase in shoot and root length was observed in P. fluorescens treated plants. The isolates of P. fluorescens systemically induced resistance against Fusarium wilt of chickpea caused by Fusarium. oxysporum f.sp. ciceri (FocRs1), and significantly (P = 0.05) reduced the wilt disease by 26-50% as compared to control. Varied degree of protection against Fusarium wilt was recorded with chemical inducers. The reduction in disease was more pronounced when chemical inducers were applied with P. fluorescens. Among chemical inducers, SA showed the highest protection of chickpea seedlings against wilting. Fifty two- to 64% reduction of wilting was observed in soil treated with isolate Pf4-92 along with chemical inducers. A significant (P = 0.05; r = -0.946) negative correlation was observed in concentration of salicylic acid and mycelial growth of FocRs1 and at a concentration of 2000 microg ml(-1) mycelial growth was completely arrested. Exogenously supplied SA also stimulated systemic resistance against wilt and reduced the disease severity by 23% and 43% in the plants treated with 40 and 80 microg ml(-1) of SA through root application. All the isolates of P. fluorescens produced SA in synthetic medium and in root tissues. HPLC analysis indicated that Pf4-92 produced comparatively more SA than the other isolates. 1700 to 2000 nanog SA g(-1) fresh root was detected from the application site of root after one day of bacterization whereas, the amount of SA at distant site ranged between 400-500 nanog. After three days of bacterization the SA level decreased and was found more or less equal at both the detection sites.
authors.affiliation: Laboratory of Applied Mycology, Centre of Advanced study in Botany, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Ratul
authors.initials: R
authors.lastname: Saikia
authors.forename: Tanuja
authors.initials: T
authors.lastname: Singh
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Juhi
authors.initials: J
authors.lastname: Srivastava
authors.forename: Alok K
authors.initials: AK
authors.lastname: Srivastava
authors.forename: Kiran
authors.initials: K
authors.lastname: Singh
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Arora
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D029863:Cicer / Q000254:growth & development / Q000382:microbiology*; D005670:Fusarium / Q000254:growth & development / Q000472:pathogenicity*; D025282:Mycelium / Q000254:growth & development; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D011551:Pseudomonas fluorescens / Q000502:physiology*; D020156:Salicylic Acid / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D020156:Salicylic Acid