الفهرس 
Chapter (1) : General IntroductionOnly 14 pages are availabe for public view
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Abstract
Prompted by the great potential of Trichoderma spp. in the field of biological control and the great loss of postharvest pathogens in crops, the aim of this study was screening of four Trichoderma spp. and eleven of postharvest tomato fungal pathogens in their capability of producing lytic enzymes (chitinase, cellulase, pectinase and xylanase) in addition to the antagonistic activity of Trichoderma spp. against the tested fungal pathogens, and studying the genetic diversity and DNA fingerprint of isolates by PCR-RAPD and ISSR techniques, in order to identify the variation and studying genetic distance between fungal isolates. Therefore, might help in; evaluation the biocontrol potential of Trichoderma strains and overcome the great loss caused by pathogenecity of postharvest fungal tomato pathogen.
So the following points were studied:
A) Antagonistic potential of Trichoderma spp. against the tested postharvest pathogenic Fungi: T. pseudokoningi (T18), T. harzianum (T24), T. harzianum (T31), T. harzianum (T39) isolates were tested for their antagonistic activity in vitro against Rhizopus oryzae and Aspergillus flavus (Af1)
b) In vitro dual culture method and the antagonistic activity were performed.
c) Production of volatile compounds was investigated on agar plates in the antagonistic action.
d) A semi-quantitative method (the Enzymatic Index, EI, on agar plates) of the four types of hydrolytic enzymes (chitinase, cellulase, pectinase and xylanase) have been investigated.
e) A quantitative method (the amount of reducing sugars, RS in liquid medium) of the four types of hydrolytic enzymes (chitinase, cellulase, pectinase and xylanase) has been measured. Isolates were compared in enzymes production.
f) Genetic diversity and DNA fingerprinting of isolates using RAPD and ISSR techniques were investigated to identify variability and study the genetic distance between fungi isolates.
The results showed the following:
• Trichoderma has shown a different pattern of antagonism against tested pathogens, biocontrol (T18, T24, T31 and T39) do not show an inhibitory zone against pathogenic fungus Rhizopus, however they were able to overgrow the pathogen 100% after 10 days of incubation. On the other hand, although there was a clear zone between the colony of the biocontrol and Aspergillus flavus (1), Trichoderma failed to grow exponentially on Aspergillus flavus.
• Tests of production volatile compounds revealed that Trichoderma inhibited growth of the two tested phytopathogens.
• Enzymes production in liquid medium or agar plates in presence of the appropriate carbon source showed that antagonists were higher in enzyme production than the tested phytopathogens, in addition Trichoderma harzianum (T24) was the most producer.
• It was concluded that, the strains of biocontrol agents were superior in their productivity of hydrolytic enzymes than pathogenic fungi, either in the liquid medium or on solid agar plates.
• Enzyme production in liquid medium showed the same pattern of enzyme production on solid agar plates.
• Values of Enzymatic Index (EI) (the enzymatic halo/colony diameter, EI = Øh/Øc) determined for each taxon might be in a similar range or varied over a wide interval of the same species either for antagonists or phytopathogens.
• It is concluded from this study that the quantitative parameter of measuring reducing sugars is more suitable than EI for evaluation of the total enzymatic activity of the tested filamentous fungi.
• Our results suggest and revealed the activity of enzyme on agar should be depend on the enzymatic halo which reflects the real enzymatic degradation activity and independent on clear zone of degradation only. In addition, Enzymatic Index (EI) should be reconsidered as a simple and rapid method for screening and selection of potent strains in enzyme production.
• In the present work, most of the tested fungal isolates of either antagonists or postharvest pathogens showed the ability to produce the four evaluated enzymes, on agar plates (mostly EI more than 1) or in liquid cultures proving their potential for industrial applications
• Levels of enzyme production were not correlated with fungal growth which corresponded as dry weight either for antagonist or phytopathogen.
• The results of RAPD analysis showed that out of 113 DNA-bands, 3 were conserved among 15 isolates of the tested fungi, while 110 (96.83%) were polymorphic.
• The Primer OPA15 amplified highest number of DNA bands (27 bands), while the OPY05 primer amplified the lowest number 18 bands.
• Unique DNA fragments with different lengths were detected in A. nidulans, A. flavus (1), A. niger (1), A. niger (3), Trichoderma (24), F. oxysporum, Alt. alternata (1), Alt. alternata (2) and P. steckii using RAPD primers.
• The primer OPA09 showed the highest PIC value 0.36 while the primer OPA15 showed the highest vales for MI and RP (9.32 and 14.13 respectively).
• The dendrogram based on RAPD data showed the genetic similarity among 15 isolates ranged from 0.32 to 0.76 with an average 0.54