الفهرس 
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Abstract
Early blight is a common tomato disease caused by several species of Alternaria )A. solani, A. tomatophila and A. alternata(. It can affect almost all parts of the tomato plants, including the leaves, stems, and fruits. The plants may not die, but they will be weakened and will set fewer tomatoes than normal. It is causing great losses in tomato production. The present investigation was planned to control EB diseases by studying the susceptibility of different cultivars to EB disease and using safe means such as biological control
Results of this work can be summarized in the following:
1. Forty-eight fungal isolates were obtained from naturally diseased tomato plants showing symptoms of early blight disease collected from different localities of Assiut and Sohag Governorates. Pathogenicity test of these isolates revealed that all tested isolates were able to infect tomato plants (cv 844) with a different degree of disease severity causing EB disease. Isolate No. 6, 20 and 31 caused the highest disease severity.
2. The highly pathogenic isolates No. 6, 20 and 31 were selected for molecular identification using ribosomal region ITS-rDNA sequencing. The isolate No.6 was identified as A. solani strain AUMMC 14485 and deposited in the GenBank and assigned with the accession number MT444991. Isolate No. 31 characterized as A. alternata strain AUMMC 14486 and placed in the GenBank nucleotide sequence database under accession number MT777510. Isolate No. 20 identified as Curvularia lunata AUMMC 14229 and was registered in GenBank with an accession number MT444990. This is the first report for C. lunata as causal pathogen EB of tomato in Egypt.
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3. Five tomato cultivars (65015 (cv 1), Basma (cv 2), Dalia (cv 3), 320 (cv 4) and 844 (cv 5) were tested for their susceptibility to EB caused by A. solani, A. alternata, and C. lunata. The results showed that cv 1 was highly tolerance to early blight disease whereas cv 4 followed by cv 5 was most susceptible to it, cv 3 and cv 2 showed moderate effect.
4. The physiological assessments of some of the tomato cultivars following exposure to EB the results observed that the causal pathogens decreased the total chlorophyll contents of the tomato cv 5 followed by cv 4 and the least effect in cv 1. However, they caused the greatest accumulation of hydrogen peroxide, superoxide anions, and lipid peroxidation. The pathogenic fungi also significantly stimulated the synthesis of ASA, GSH, SA, soluble phenolic compounds, PAL, and PPO in all the infected tomato cultivars except cv 4 or cv 5, with cv 1 showing the greatest changes 5. Histopathological studies of the infection phases of A. solani and C. lunata on the highly tolerance cultivar cv 1 and the highly susceptible cultivar cv 5 under the light microscope demonstrated that the leaves of cv 1 were coated with thick epidermal hairs and glandular hairs and had relatively few stomata, whereas those of cv 5 had a limited number of hairs and many stomata. Electron microscopy further showed that the fungal mycelia of A. solani or C. lunata easily attacked the open stomata of the hypersensitive cultivar cv 5 but they did not attack the open stomata of cv 1. The findings indicate that physiological and histopathological studies of various cultivars could be one of the methods used to detect the restraint of tomato plant cultivars to early blight disease.
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6. Twenty isolates of endophytic bacteria isolated from each part of healthy tomato plants (root, leaves and stem) were tested in vitro against growth of pathogenic isolates (A. solani, A. alternata, and C. Lunata). All tested endophytic bacterial isolates were able to inhibit the growth of fungal pathogens with different degrees (c/m) compared with control. Endophytic isolates No. 1, 4, 7, 8, 10, 14, 15, 17 and 18 showed highest inhibition growth of fungal pathogens. Isolates No. 4, 7 and 17 were selected based on morphological and microscope study for further study.
7. The selected bacterial isolates (No. 4, 7 and 17) were identified using 16s-rRNA. The resulted sequences of tested isolates identified as Enterobacter cloacae HS-6, Pseudomonas gessardii HS-5 and P. mediterranea HS-4 respectively. They preserved in the GenBank under the accession number MT444991, MT520143 and MT520147.
8. The activity of culture filtrates (CF-Ec, CF-Pg and CF-Pm) of antagonistic bacterial isolates (E. cloacae (Ec), P. gessardii (Pg) and P. mediterranea (Pm) respectively) was tested at different concentrations (20, 40 and 60%) against the growth of fungal pathogens. According to the results, the concentrations of bacterial filtrates were decreased the dry weight of pathogenic fungi compared with control. All bacterial filtrates at 60% showed the lowest dry weigh of pathogenic isolates followed by 40% and then 20%. The CF-Ec showed the lowest dry weigh of pathogenic isolates followed by CF-Pg and then CF- Pm.
9. Analysis of bacterial culture filtrates (CF-Ec, CF-Pg and CF-Pm) were carried out using Gas chromatography and mass spectroscopy. GC-MS analysis of CF-Ec revealed that the existence of twenty-five compounds (VOCs). The highest peak area of CF-Ec was identified
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as Phenol, 2,4-di-tert-butyl- or Phenol, 2,4-bis (1,1-dimethylethyl)- and 2-Butanone, 3-hydroxy-(ç-Hydroxy-á-oxobutane). The CF-Pg contains twenty VOCs. Phenol, 2,4-bis (1,1-dimethylethyl)- or Phenol, 2,4-di-tert-butyl showed a highest peak area. The analyses of CF-PM observed 20 VOCs. Phenol, 2,4-bis (1,1-dimethylethyl)- or Phenol had the largest peak area.
10. The antagonistic bacterial isolates (Ec, Pg and Pm) and their cultural filtrate (CF-Ec, CF-Pg and CF-Pm) at 60 % were tested on incidence of EB disease on tomato under greenhouse conditions. All tested bacterial isolates and their culture filtrates significantly decreased the disease severity percentage with varied degrees. The least disease severity of EB found with Ec followed by Pg and then Pm. Spraying infccted plants with CF-Ec reduced EB more than CF-Pg, but CF-Pm had the least effect on EB. Ec and its culture filtrate (CF-Ec) had a similar effect on disease severity reduction. However, there were variations between suspensions of Pg and Pm and their filtrates on disease severity reduction.
11. In two growing seasons (2018 and 2019), the effect of antagonistic bacteria and their culture filtrate on the severity of EB disease was studied under field conditions. The findings from field experiments matched with the greenhouse results. However, in case of Pg and its CF-Pg showed a similar effect on the reduction of the EB disease. This outcome was the opposite from greenhouse experiment.
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