Effectiveness of some biotic and abiotic agents to control tomato early blight disease caused by Alternaria solani

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.

Evaluation of the Efficacy of some Bioagents accompanied with Bio- and Mineral Fertilizers in Controlling Early Blight of Tomato and Improvement Yield

“…In addition, Khalil and Adbelghany (2021) indicated that T. harzianum was the best bioagent, which inhibited the growth of A. solani, Data of this study showed that phenol components were increased with using the biofertilizer and the bioagents more than with mineral fertilizer during the two seasons. These results are in agreement with those reported by Khalil and Adbelghany (2021) who found that treated tomato plants with the bioagents led to an increase in the total dissolved phenols in tomato leaves compared to the control. The highest significant increase in the total dissolved phenols in tomato leaves was obtained from tomato plants treated with T. harzianum.…”

“…Agricultural fungicides combat plant pathogens: but they have negative effects on the beneficial natural organisms. Therefore, it is necessary to develop environmentally friendly and biodegradable agricultural alternatives in order to control plant pathogens (Khalil and Adbelghany, 2021). So, the use of bioagents has become important as an alternative to fungicides to prevent postharvest losses in recent years.…”

Native Rhizospheric Microbes Mediated Management of Biotic Stress and Growth Promotion of Tomato

“…Each washing was performed for 15 min at 4 • C for the removal of the unreactive fixatives. Then, the sections were dehydrated for 20 min in each graded series of ethanol (30,50,70,90,95, and 100%). The sections were dried at critical point drying and then mounted on an aluminum stub with carbon tape.…”

“…Effective root colonization aids microbes in inducing ISR efficiently and, thus, help them to render pathogens, including those that infect plants at spatially different locations [17,[22][23][24]. Trichoderma, Pseudomonas, Bacillus, and arbuscular mycorrhizal fungi (AMF) are some microbial isolates that have the potential to abridge plant stress [12,19,[25][26][27][28][29][30]. For instance, the application of compost containing Bacillus subtilis QST713 and Trichoderma sp.…”