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Isolation and characterization of some bacteria antagonistic to plant pathogenic fungi


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Oedjijono, 1992 , 'Isolation and characterization of some bacteria antagonistic to plant pathogenic fungi', Unspecified thesis, University of Tasmania.

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

Item Type: Thesis - Unspecified
Keywords: Plants, Pathogenic fungi, Antibiosis
Copyright Holders: The Author
Copyright Information:

Copyright 1992 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references (leaves 137-169). Thesis (M.Sc.)--University of Tasmania, 1993

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