الفهرس 
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Abstract
”One of the problems that affect cultivation of the plants in Egypt and the world is exposing to infection with many diseases especially fungal diseases. Wilt diseases caused by Fusarium oxysporum is the most abundant disease of fungal diseases as it leads to a high loss in the crop under certain environmental conditions. The farmers tend to use chemicals to control this disease but, the intensive use of these chemicals has adverse effects on humans and ecosystem functioning as reducing agricultural sustainability, being long persistence, in addition many of these chemicals are too expensive for the poor farmers and some fungi develop resistance to a number of chemicals, some research had been done on using biological control to control wilt disease. Therefore, this study aimed to replace the undesirable and unsafe chemical control by other safe and effective way for controlling wilt disease. Soil infestation of biocontrol agent was suggested to overcome this problem and provide acceptable control level of wilt disease. In this study, forty-two fungal species belonging to sixteen genera namely: Alternaria, Aspergillus, Botrytis, Cercospora, Circinella, Cladosporium, Cunninghamella, Drechslera, Fusarium, Glieocladium, Mucor, Nigrospora, Pencillium, Rhizopus, Stachybotrys and Trichoderma were isolated from twenty-five different plant species these were: Anise, Arugula, Bean, Basil, Celery, chrysanthemum, Crane’sbill, Clove, Coriander, Corn, Cucumber, Cumin, Dill, Garlic, Mentha, Onion, Pepper, Potato, Pumpkin, Radish, Ricinus, Rosemary, Sunflower, Thyme, and Tomato. The most dominant and frequent genera were Aspergillus represented by one hundred fifty-two isolates belonging to seven species and Alternaria by ninety-four isolates belonging to five species. The most frequent species was A. ochraceus. The highest number of endophytic fungal species was recorded in Anise represented by nine species, followed by Ricinus and Thyme (7 species for each), Pepper (6 species). Moreover Cucumber, Crane’s-bill, Bean and Potato recorded the same number of endophytic fungal species (5 species for each) followed by clove (4 species) while each of Pumpkin, Sunflower, and Rosemary recorded (3 species for each). On the other hand, two species were recorded in each of Cumin, Coriander, Celery, chrysanthemum, Corn, Onion, Radish, and Tomato while Dill and Garlic recorded one species only. Five isolates of F. oxysporum were isolated from different wilted plants. Pathogencity test was made on healthy Tomato, Potato, and Cucumber plants to determine the most aggressive isolate. The study showed that all isolates had the ability to cause Fusarium wilt disease on tested plants and the isolate No.3. of F. oxysporum f. sp. cucumerinum, was the most aggressive isolate, giving the highest percentage of disease incidence (73.8%) and severity index (6). Therefore, isolate No.3 was selected for further studies. To ensure the validity of endophytic fungi to inhibit growth of Fusarium oxysporum, dual culture experiment was made (antagonism). Of all the tested endophytic fungal isolates twenty-four isolates showed significant inhibitory effect on the mycelial colony growth of the pathogen, while nine of them were the most potent antagonists especially Trichoderma viride where it suppressed the colonization of F. oxysporum with 90% after eight days in comparison with control plates (F. oxysporum only). The nine selected endophytic fungal isolates and fungal pathogen were subjected to molecular identification based on 18S rRNA. The phylogenetic tree illustrated the fungal strains as follow: Alternaria alternata MT991480, Aspergillus flavus ON171640, Aspergillus ochraceous FJ427513, Cunninghamella elegans JQ228241, Fusarium oxysporum DQ916150, Trichoderma hamatum NR134371, Trichoderma harzianum ON242100, Trichoderma kongngii NR138456, Trichoderma reesei NR120297 and Trichoderma viride KY346987. Culture filtrate, methanolic and ethyl acetate extract of selected endophytic fungi possessed antifungal activity and inhibited growth and sporulation of F. oxysporum, but Trichoderma viride was the most effective, so the results obtained from dual culture test and antifungal test indicate that Trichoderma viride was the most potent biocontrol agent used against the pathogen. Trichoderma viride was chosen to study its effect on linear growth, mycelial dry weight and spore germination of the tested phytopathogenic fungus by using different concentrations (10%, 20%, 30%, 40%, 50%, 60%, 70% and 80%) of crude culture filtrate and (0.25 mg/ml, 0.5 mg/ml, 1 mg/ml, 2 mg/ml, 4 mg/ml , 6 mg/ml , 8 mg/ml and 10 mg/ml) of methanolic and ethyl acetate extracts. The study revealed that culture filtrate at concentration (80%), methanolic and ethyl acetate extract at concentration (10mg/ml), the mycelial linear growth, dry weight, and spore germination of F. oxysporum f. sp. cucumerinum were significantly decreased. The miniumum inhibitory concentrations (MICs) of crude culture filtrate of Trichoderma viride demonstrated antifungal efficiency against F. oxysporum f. sp. cucumerinum recorded 30% while, ethyl acetate and methanolic extracts recorded 0.50 mg/ml and 1.00 mg/ml respectively. The greenhouse experiment was conducted to evaluate the effect of Trichoderma viride culture filtrate (80%) and fungicides Rhizolex-T (3g/l) on cucumber plants infected with F. oxysporum f. sp. cucumerinum.
The treatments of cucumber plants with biocontrol agent Trichoderma viride was effective on reduction the Fusarium wilt diseases severity and disease incidence followed by fungicides Rhizolex-T comparing with artificial infected plant. Moreover, the results demonstrated that, the infection of cucumber plants with F. oxysporum f. sp. cucumerinum reduced the growth parameters as (shoot and root length, shoot and root fresh and dry weight, number of leaves and leaf area) and photosynthetic pigment. On the other hand, it caused a marked increase in the total phenol content, defence related enzymes; (POD, PPO, and PAL), lipid peroxidation; (MAD) and hydrogen peroxide; (H2O2) as compared with healthy plant. Furthermore, plants treated with the used bioagent showed a marked increase in these variables indicating its important role in biocontrol. The microscopic characterization of the fungus Trichoderma viride and F. oxysporum f. sp. cucumerinum was accomplished to determine the mechanism of inhibition. The antagonistic process that occurs between T. viride and FOC is due to the competition that occurs between the two fungi grown side by side and mycoparasitism.