الفهرس 
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Abstract
Tomato is an important commercial crop in the world. Sensory and nutritional characteristics make it a widely accepted vegetable by consumers. Tomato is grown in most countries of the world, being Asia the largest producer. The area devoted to tomato cultivation is estimated to be 3 million hectares in the world.
The cultivated area of tomato in Egypt is progressing at a relative fast rate, especially in newly reclaimed desert lands. According to Economical Statistic Report, Agriculture Statistic, Economic Affairs Sector (Vegetable Crops), August, 2015, Ministry of Agriculture and Land Reclamation, ARE, cultivated area of tomato was 509562 fadden, yielded 8264543 tons, with average of 16.912 tons / fadden.
Many fungal diseases attack Tomato plants during growing season and cause economic loss in cropping fruit yield as well as the large losses in field. The root rot diseases are very important and cause great loss in fruit yield. These trials were conducted to study the causal organisms of root rots and their control. Results can be concluded as follows:
1. Tomato plant showing typical root rot symptoms were collected from 6 governorates of Egypt (Beheira, Giza, Ismailiya, Qalubiya, Qena and Sharkiya). These samples were used for isolation of the causal organisms from diseased tomato plant materials.
2. Two hundred and fifty nine fungal pathogens were isolated from the diseased roots during 2012 and 2013 seasons. Data indicated that
Alternaria solani was most frequent fungus was isolated from root of tomato plant but least frequent fungus was Paecilomyces spp.
3. Twenty fungal isolates out of 259 were tested for their virulence using tomato roots of (GF12/ the most susceptible tomato cultivar) were used in Pathogenicity test. Data indicate that all tested isolates were pathogenic to tomato roots under greenhouse conditions. Significant differences were noticed between unwounded and wounded roots. The most aggressive isolate was Alternaria solani isolate 1 followed by Rhizoctonia solani followed by Fusarium oxysporium isolate 1, whereas the lowest percentage of infection was obtained by Camarosporum tassi and R. oryzae.
4. Twenty bioagents belong to Trichoderma spp; T. hamatum (5 strains), T. harzianum (5 strains), two strains from each of T. atroviride, T. longbactrium, T. reesei and T. viride and one strain from each of T. koningii and T. virens were isolated from soil and rhizosphere samples were taken selected from tomato fields by uprooting the infected plants.
5. The best control was recorded by T. harzianum Tz1, T. koningii Tk1, T. longbactrium Tl1 and T. viride Td1 are selected as the most potent bioagents that controlled the aggressive pathogens causing tomato root rot disease under laboratory and greenhouse conditions.
6. The four Trichoderma spp were exposed to different doses of gamma radiation (0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5 and 5.0 kGy).
7. The resistance of selected Trichoderma species to gamma irradiation was increased in the following pattern; T. viride Td1 > T. harzianum Tz1 > T. koningii Tk1 > T. longbactrium Tl1. Consequently, the D10 values were 0.752, 0.739, 0.663 and 0.563 kGy in the same order.
8. After exposing of different bioagents (belong to Trichoderma spp) to increasing doses of gamma irradiation, the growing colonies that survived to the sub-lethal irradiation dose were selected, purified, symbolized and maintained as first generation variants.
9. These variants were further exposed to higher irradiation doses (More than sub-lethal dose). The spore suspension of T. harzianum to (4.0, 4.5, 5.0 and 5.5 kGy), T. koningii to (4.5, 5.0, 5.5 and 6.0 kGy), T. longibrachiatum (3.5, 4.0, 4.5 and 5.0 kGy) and T. viride were exposed to (5.0, 5.5, 6.0 and 6.5 kGy).
10. Three second generation variants of T. harzianum Tz1 succeeded to grow after irradiation with 5.5 kGy; they are Tz1/1-3, Tz1/3-3, Tz1/4-3 but only one variant could not grow at this dose; 5.5 kGy (Tz1/2-2). Similarly, three second generation variants of T. koningii Tk1 could grow after irradiation with 6.0 kGy (Tk1/2-3, Tk1/3-3, Tk1/4-3) whereas variant (Tk1/1-2) stop growing at 5.5 kGy or higher doses. The less resistant second generation variants are belonging to T. longbactrium since variant symbolized Tl1/2-2 failed to grow at 5.0 kGy dose or higher. The other variants of T. longbactrium (Tl1/1-3, Tl1/3-3, and Tl1/4-3) could grow up to 5.0 kGy.The most potent
resistant variants are belonging to T. viride Td1/1-3 and Td1/2-3; they keep alive after irradiation with 6.5 kGy.
11. These thirty-nine second generation variants as well as their first generation fourteen variants that could grow at the sub-lethal irradiation doses are selected. The antagonistic activities of these variants against the selected fungal pathogens causing tomato root rots were studied in comparison with their parents in upcoming experiments under laboratory conditions.
12. Selcteted two variants of Trichoderma harzianum (Tz1/1-3, Tz1/4-3), two variants of T. koningii (Tk1/2-3, Tk1/3-3), two variants of T. longbactrium (Tl1/3-3, Tl1/4-3) and one variant of T. viride (Td1/2-3). Their antagonistic activity against tomato root rot fungal pathogens under greenhouse conditions are studied as well as their first generation variants (Exposed once to gamma irradiation) and their parent strains.
13. The antagonistic activity of second generation variants is higher than first generation variants and the activity of first generation variants is higher than their parent strain, i.e. exposing different bioagents to gamma irradiation increase their antagonistic activity against A. solani, R. solani and F. oxysporum under greenhouse condition.
14. The effect of volatile compounds produced by Trichoderma spp and their irradiated variants on controlling tomato root rot pathogens were studied medium under laboratory conditions.
15. The potency of volatiles compounds evolved from second generation variant of T. viridi Td1/2-3 after exposed twice to gamma irradiation; 5.0 followed by 6.5 kGy to control selected root rot causing pathogens under laboratory conditions.
16. The volatile compounds produced by T. viridi as well as its irradiated variants (first and second generation) were subjected to analysis using GC/MS. The most abundant volatile evolved from T. viridi Td1 (parent strain) was 3- [(á, á- Dimethyl- à- styryloxy) - dimethylsilyloxy] -2 -pentene (74.91%), T. viride Td1/2 (second strain) was Silane, diethoxydimethyl - (CAS) (43.47%) and T. viridi Td1/2-3 (second generation) was (3R) -3 -Phenyl- 2, 3- dihydro-1 H-isoindol-1-one (27.16%).
17. To control tomato root rot caused by selected fungal pathogens using volatile compounds, two strategies were applied in individually experiments. One of them based on exposing tomato seeds directly with volatile compounds and another is treating the fungal pathogens to these compounds under greenhouse conditions.
18. Monitoring the extra cellular enzymes for selected Trichoderma bioagents and their variants originate using gamma irradiation. Most irradiated variants showed an increase in lytic enzymes compared to their parent strains the production of cellulase and chitinase yield achieved by second generation variants T. koningii TK1/2-3 and T. harznium Tz1/1-3, respectively.
19. Crude cellulase at 100 mg/ml succeeded to decrease the radial growth of A. solani and F. oxysporum by nearly 20%. R. solani showed the highest sensitivity against crude chitinase in comparison to other tomato root rot fungal pathogens under laboratory conditions.
20. Both of pre and post-emergence percentages of tomato damping- off were decreased by coating tomato seeds GF12 with crude cellulases extracted from the second generation variant of T. koningii TK1/2-3. On the same trend, the number of survival plants increased while the disease index was decreased to minimum values under greenhouse conditions.
21. when tomato seeds were coated with crude chitinase extracted from the second generation variant of T. harznium Tz1/1-3; the percentage of pre-emergence damping-off decreased to 5.0% whereas the percentage of post-emergence damping-off caused by root rot pathogen; A. solani was decreased to zero. Similarly, the disease index was decreased to nearly half while the number of survival tomato plants increased up to 35 or higher under greenhouse conditions.
22. Monitoring peptides yield for selected Trichoderma bioagents and their variants originate using gamma irradiation. The highest peptide yield was achieved by the second generation of T. koningii Tk1/3-3 variant after exposure to 6.0 kGy.
23. Crude peptide produced by parent strain of T. koningii Tk1, its first generation variant Tk1/3 and its second generation variant were
purified by column chromatography using silica gel 70-230 mesh. Peptide of parent strain of koningii Tk1 was fractionated into eleven fractions, the first generation variant T. koningii Tk1/3 their number is decreased to nine while the second generation variant Tk1/3-3 was partially purified into four fractions.
24. The antagonistic activity of partially purified fractions of peptides extracted from parent strain of T. koningii and its variants against tomato root rot pathogens were assayed in individual experiments. The most active peptides fractions is fraction (4) produced by second generation T. koningii variant Tk1/3-3. It declines the radial growth of three selected tomato root rot pathogen by nearly 40% and 50% at 50 and 100 ppm; respectively.
25. In a greenhouse experiment, Crude peptides completely succeeded to control damping-off caused by tomato root rot pathogens by nearly 100% while the disease index decreased by nearly half.