Document Type : Original Article
Authors
Plant Pathology Research Institute, Agricultural Research Center, 12619 Giza, Egypt.
Abstract
Bacillus megaterium, Bacillus subtilis, Pseudomonas fluorescens, Trichoderma harzianum, Trichoderma album and Trichoderma viride isolates, as well as different concentrations of chemical inducers, such as chitosan and salicylic acid were evaluated against Tomato early blight, under laboratory and greenhouse conditions. Under laboratory conditions, all tested bio agents, as well as the different concentrations of the tested chemical inducers, decreased the linear growth of A. solani, as the inhibition of fungal growth was increased by increasing the concentration of both chemical inducers in the growing medium. The chemical inducer chitosan at a concentration of 4.0 mg/mL PDA medium, caused the highest inhibition of linear growth of the fungus, followed by anti-fungus T. harzianum. When, different concentrations of chitosan and salicylic acid were tested on spore germination of A. solani, a concentration of 4.0 (mg/mL), for chitosan and a concentration of 25.0 (mM), for salicylic acid were the best concentrations used to reduce the spore germination of A. solani. Under greenhouse conditions, spraying tomato plants (cv. Super Strain B hybrid), with any of the tested biological agents as well as different concentrations of both the chemical inducers before infection of tomato plants by A. solani reduced the severity of early blight, in addition, to increase the fresh and dry weight of tomato plants. The chemical inducer chitosan at a concentration of 4.0 (mg/mL), caused the highest decrease of the disease severity, and the highest increase in fresh and dry weight of tomato plants, followed by the bio agent T. harzianum. The activities of defense-related enzymes i.e., polyphenoloxidase, peroxidase and chitinase were significantly increased in all treated plants with the tested biotic and abiotic agents. Chitosan at a concentration of 4.0 (mg/mL) resulted in the highest activity of oxidative enzymes, followed by T. harzianum. Meanwhile, the total content of phenols was higher in treated plants than in the untreated ones. The tested bio agents and chemical inducers might be playing an important role in management of tomato early blight through induction of induced systemic resistance.
Keywords
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