INDUCTION OF DEFENSE RESPONSES IN TOMATO PLANTS INOCULATED WITH PHYTOSTIMULATION MICROORGANISMS AGAINST Fusarium oxysporum
2005
M. Attia, | Hamed Hoda A.
Phytostimulation microorganisms (PSM) viz. Trichoderma harzianum (TH), Bacillus subtilis (BS) and arbuscular mycorrhizal (AM) fungi were tested individually or in mixed culture for their ability to induce pathogenesis-related (PR)-proteins (chitinase, β-1,3-glucanase, peroxidase, phenylalanine ammonia-lyase PAL) and phenolics in tomato plants grown in sterilized soilless medium artificially infested with or without the Fusarium oxysporum f. sp. radicis-lycopersici (FORT). PSM-treated plants were more developed than non-treated control or inoculation with FORT. PSM-treated plants were effective in reducing diseases produced by FORT infection. Plants application with PSM significantly increased the activity of peroxidase, chitinase, β-1, 3-glucanase and PAL and accumulated phenolics in tomato plants compared to untreated control. Among the treatments, AM fungi recorded the maximum increase in the activities of all defense–related enzymes and accumulated phenolics followed by T. harzianum and B subttilis. The maximum increase in the activities of peroxidase, β-1, 3- glucanase, PAL and accumulated phenolics were observed 6 days after application of PSM. However, the maximum increase in the activities of chitinase was observed 9 days after application of PSM. Several fold increase in the accumulation of phenolics and activities of defense enzymes was observed when the induced plants were inoculated with Fusarium oxysporum f. sp. radicis-lycopersici (FORT). These results suggest that enhanced activities of defense enzymes and elevated content of phenolics by inoculation with PSM may contribute to protection of tomato plants against F. oxysporum.
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