Trichoderma harzianum enhances the production of nematicidal compounds in vitro and improves biocontrol of Meloidogyne javanica by Pseudomonas fluorescens in tomato.
OBJECTIVE
To determine the influence of soil-borne fungus Trichoderma harzianum on the biocontrol performance of Pseudomonas fluorescens strain CHA0 and its 2,4-diacetylphloroglucinol (DAPG) overproducing derivative CHA0/pME3424 against Meloidogyne javanica.


RESULTS
Amendment of the culture filtrate (CF) or methanol extract of the CF of a T. harzianum strain Th6 to P. fluorescens growth medium enhanced the production of nematicidal compound(s) by bacterial inoculants in vitro. In addition, bacteria overwhelmingly expressed phl'-'lacZ reporter gene when the medium was amended with CF of T. harzianum. Pseudomonas fluorescens and T. harzianum applied together in unsterilized sandy loam soil caused greater reduction in nematode population densities in tomato roots.


CONCLUSIONS
Trichoderma harzianum improves root-knot nematode biocontrol by the antagonistic rhizobacterium P. fluorescens both in vitro and under glasshouse conditions.


CONCLUSIONS
The synergistic effect of T. harzianum on the production of nematicidal compound(s) critical in biocontrol may improve the efficacy of biocontrol bacteria against plant-parasitic nematodes. Considering the inconsistent performance of the biocontrol agents under field conditions, application of a mixture of compatible T. harzianum and P. fluorescens would more closely mimic the natural situation and might broaden the spectrum of biocontrol activity with enhanced efficacy and reliability of control.
Siddiqui
I A
IA
Soil Biology and Ecology Laboratory, Department of Botany, University of Karachi, Karachi, Pakistan. imran_75850@yahoo.com
Shaukat
S S
SS
D000818:Animals; D000969:Antinematodal Agents / Q000378:metabolism* / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D018551:Solanum lycopersicum / Q000469:parasitology*; D010572:Pest Control, Biological / Q000379:methods*; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000378:metabolism; D018517:Plant Roots / Q000469:parasitology; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism*; D012988:Soil Microbiology; D014242:Trichoderma / Q000502:physiology*; D014431:Tylenchoidea / Q000254:growth & development*; D001616:beta-Galactosidase / Q000378:metabolism
D000969:Antinematodal Agents; C059817:2,4-diacetylphloroglucinol; D010696:Phloroglucinol; D001616:beta-Galactosidase