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Biological Control of Tomato Bacterial Leaf Spots and Its Impact on Some Antioxidant Enzymes, Phenolic Compounds, and Pigment Content
by
, , and
Asmaa H. Akila
1,
Mohamed A. S. Ali
1,
Ahmed M. Khairy
1,
Ahmed S. M. Elnahal
1,*,
Haifa E. Alfassam
2,*,
Hassan A. Rudayni
3,
Fatima A. Jaber
4 and
Mohamed R. A. Tohamy
1 1
Plant Pathology Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt
2
Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia
3
Department of Biology, College of Science, Imam Mohammad Ibn Saud Islamic University, Riyadh 11623, Saudi Arabia
4
Department of Biological Sciences, College of Science, University of Jeddah, Jeddah 21589, Saudi Arabia
*
Authors to whom correspondence should be addressed.
Biology 2024, 13(6), 369; https://0-doi-org.brum.beds.ac.uk/10.3390/biology13060369
Submission received: 16 February 2024
/
Revised: 17 May 2024
/
Accepted: 18 May 2024
/
Published: 23 May 2024
Simple Summary
Tomato bacterial spots and specks, caused by various strains of Xanthomonas campestris and Pseudomonas syringae, lead to significant yield losses in the El-Sharkia governorate. This study tested the efficacy of biocontrol culture filtrates from Trichoderma fungi (T. viride, T. harzianum, T. album) and bacterial agents (Bacillus subtilis, Pseudomonas fluorescens, Serratia marcescens) in controlling these diseases. In vitro, the culture filtrates significantly inhibited pathogenic bacterial growth. In vivo, spraying bioagents prior to infection reduced disease incidence and severity. T. viride was the most effective fungal bioagent, while B. subtilis was the top bacterial bioagent. Tomato plants that were treated with bioagents also had more phenols and chlorophyll than control plants. They also had more enzyme activity, including chitinase, peroxidase, and polyphenol oxidase. These findings suggest that biocontrol strategies could be a sustainable solution for managing tomato diseases and improving plant defense.
Abstract
Tomato bacterial spots, caused by Xanthomonas campestris pv. vesicatoria (Xcv1) and X. euvesicatoria (Xe2), as well as bacterial specks, caused by two strains of Pseudomonas syringae pv. tomato (Pst1 and Pst2), represent significant threats to tomato production in the El-Sharkia governorate, often resulting in substantial yield losses. The objective of this study was to evaluate the efficacy of various biocontrol culture filtrates, including bacteria and fungi agents, in managing the occurrence and severity of these diseases, while also monitoring physiological changes in tomato leaves, including antioxidant enzymes, phenolics, and pigment content. The culture filtrates from examined Trichoderma species (T. viride, T. harzianum, and T. album), as well as the tested bacteria (Bacillus subtilis, Pseudomonas fluorescens, and Serratia marcescens) at concentrations of 25%, 50%, and 100%, significantly inhibited the proliferation of pathogenic bacteria In vitro. For the In vivo experiments, we used specific doses of 5 mL of spore suspension per plant for the fungal bioagents at a concentration of 2.5 × 107 spores/mL. The bacterial bioagents were applied as a 10 mL suspension per plant at a concentration of 1 × 108 CFU/mL. Spraying the culture filtrates of the tested bioagents two days before infection In vivo significantly reduced disease incidence and severity. Trichoderma viride exhibited the highest efficacy among the fungal bioagents, followed by T. harzianum and T. album. Meanwhile, the culture filtrate of B. subtilis emerged as the most potent among the bacterial bioagents, followed by P. fluorescens. Furthermore, applying these culture filtrates resulted in elevated levels of chitinase, peroxidase, and polyphenol oxidase activity. This effect extended to increased phenol contents, as well as chlorophyll a, chlorophyll b, and carotenoids in sprayed tomato plants compared to the control treatment. Overall, these findings underscore the potential of these biocontrol strategies to effectively mitigate disease incidence and severity while enhancing plant defense mechanisms and physiological parameters, thus offering promising avenues for sustainable disease management in tomato production.
