الفهرس 
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Abstract
The research for a new management of fungal plant disease has focused on integrated control. Therefore, there is an urgent need for development of effective biocontrol agents more resistant to fungicide to be used. In this term, some Trichoderma spp. may be used as biocontrol agents. The following results can be drawn from the study: • Six Trichoderma spp. were isolated from the rhizosphere of maize and clover at different locations (EL-Menufia and EL-Garbia) in Egypt. All tested Trichoderma spp. showed sensitivity to Rizolex T 50 % except isolates of T. harzianum and T. koningii exhibited the best tolerance to this fungicide, reached to 400 and 350ppm respectively. • T. koningii and T. harzianum were tested as biocontrol agent of plant pathogenic fungi Fusarium oxysporum, F. proliferatum and Acremonium strictum. The antagonistic effect of T. harzianum was high against pathogenic fungi, Fusarium. oxysporum, Fusarium. proliferatum and Acremonium Strictum, reached to 77.3, 77.5 and 78% reduction respectively. While, T. koningii reduced the growth of these fungi to approximately 69, 73 and 77% respectively. • Sensitivity of pathogenic fungi to Rizolex T 50% were tested on PDA and PD broth medium amended with different concentrations of Rizolex T50%. The result revealed that F. proliferatum was the most resistant fungi, it was able to grow up to 550 ppm of Rizolex T 50% on PDA medium and 250 ppm in PD broth medium. While Ac. strictum was the most sensitive fungi, it was able to grow up to 250 ppm on PDA and 50 ppm in PD broth medium. • Physical mutagenesis (using UV 254 nm) were applied on Trichoderma spp.. The result revealed that the increasing exposure time of conidia of both fungi to ultraviolet radiation leads to a decrease in the number of colonies of both fungi up to 20 min. The highly survived colonies of T. koningii and T. harzianum which were Summary 114 able to grow after exposure to high exposure time (14, 16, 18 and 20 min) were used as a mutants. • Also chemical mutagenesis (using NaN3) were applied on Trichoderma spp.. The result revealed that the number of survived spores highly decreased to low levels when NaN3 treated conidia was grown on PDA medium containing different concentrations of Rizolex T 50%, it reached to approximately 1.5% for both fungi at 70 ppm of Rizolex T 50%. The survived colonies were used as a new Trichoderma mutants • The most resistant mutants of T. harzianum named as ThMu9, ThMu8, ThMu12 and ThMu6 (UV mutant) were able to grew in the presence of Rizolex T 50% up to 1000, 900, 800 and 700 ppm respectively. While its chemical mutants were ThMc5, ThMc4 and ThMc3 were able to grew in presence of Rizolex T 50% up to 1000, 600 and 600ppm respectively. • The most resistant UV mutants of T. koningii were TkMu11 then TkMu10, TkMu12 and TkMu9 (700, 700, 600and 600ppm respectively) . Whereas its chemical mutants were TkMc5, TkMc4 and TkMc3 ( 800ppm, 700ppm and 400ppm respectively). • All the mutants of Trichoderma spp. showed high sporulation rate than the wild type except NaN3 mutant ThMc3. The sporulation of native Trichoderma spp. and their mutants decreases with increasing Rizolex T 50% concentrations in PDA medium, but the sporulation of the mutants were more than the wild Trichoderma spp. under the same concentration of Rizolex T 50%. • All the mutants of Trichoderma spp. showed higher antagonistic effect against pathogenic fungi than its native type either in absence or presence of Rizolex T 50%. Chemical mutants were more effective inhibitors than the UV mutant. NaN3 mutant of T. harzianum ThMc5 reduced the growth of pathogenic fungi, F. oxysporum, F. proliferatum and Ac. Strictum to approximately 86.6, 90.7 and 92% respectively, while its UV mutant ThMu9 reduced these fungi to 84, 82.7 and 92% respectively. On the same approach, T. koningii NaN3 mutant TkMc5 reduced the Summary 115 growth of these fungi to approximately 87.5, 87.5 and 82% respectively. Whereas, its UV mutant TkMu11 reduced them to 82.7, 83.7 and 84% respectively. Most mutants showed high antagonistic activity against Ac. strictum reached to 92%. • Utilization of low dose of fungicide in combination with mutants of Trichoderma spp. increased the inhibition percentage of pathogenic fungi than its wild type with fungicide and also in compare with Trichoderma or low concentration of Rizolex T separately. This may be beneficial in controlling these fungi. • RAPD - PCR analysis of both chemical and UV mutants and the wild type Trichoderma spp. showed different amplification patterns such as deletion or addition of DNA bands. When DNA of wild Trichoderma and its mutants amplified with primer OP-A01, OP-B07, OP-B09, OP-C02, OP-C04 and OP-C019 indicated that treatment of conidia of Trichoderma spp. with NaN3 and UV (254 nm) induced mutation. • Finally, the results of this study indicate that treatment of conidia of Trichoderma spp. with NaN3 and UV (254 nm) enhancement its biocontrol activity and its resistance to Rizolex T 50%. Also combination between low dose of Rizolex T 50% and Trichoderma mutants may be beneficial in controlling some phytopathogenic fungi.