Isolation and characterization of some bacteria antagonistic to plant pathogenic fungi

摘要: Bacteria antagonistic to plant pathogenic fungi were isolated from various sources and tested for their ability inhibit or protect plants in vitro, the glasshouse a field trial. Five strains of bacterial antagonists from daisy roots (Bacillus polymyxa UTl), decomposing woodchips (B. subtilis UT2), clary sage roots (Pseudomonas cepacia UT3 P. putida UT4) and from white clover (Acinetobacter sp. UT5). In the degree inhibition by five varied, with strain UT3 showing antagonism all fungal pathogens (Sclerotinia sclerotiorum; S. minor; Botrytis cinerea; Pythium ultimum; Fusarium solani; Phytophthora cinnamomi; cactorum; Gaeumannomyces graminis; Penicillium echinulatum) tested. The action depended on media used. Isolates of UTl inhibitory both PDA KBM; the other only PDA. Antifungal compounds produced thought be responsible for inhibiting rather than ferric-siderophores, as addition of iron did not affect activity the antagonists. The (strains UTl, UT2, UJ"3, UT4, NIR-6 P. putida) significantly reduced wheat take-all disease an axenic sand assay isolate (P. cepacia) most the pathogen. The maintained viability to protect after 3 weeks assay. glasshouse, the UTl UT5) lettuce (La.ctuca sativa) drop caused either Sclerotinia sclerotiorum minor compared controls 10 growth. field however, protect (Olearia phlogopappa) plants root rot by Pythium sp.. Metabolites produced to several vitro. Strain two types of antibiotic designated A B. Compound (the main inhibitor) was bacteria tested, while compound B (the minor inhibitor) was bacteria. main compound had Rp 0.40 minor 0.87 silica gel following development chloroform-methanol (7:3) solvent system. Both very similar retention times (between 20 22 minutes) following separation C1g reversed phase HPLC elution 0- 100% methanol containing 0.1 % trifluoroacetic acid. Both antibiotics were thermostable resistant acidic alkaline treatments. Proton NMR indicated that may aromatic molecule but further characterization possible due to incomplete purification.