الفهرس 
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Abstract
VI) Summary
In this study, filamentous fungi and yeast antagonists were isolated from the rhizosphere soil of rice plants of El- Dakahlia and El- Qaliubiya governorates and tested in vitro for control Drechslera species were isolated from infected rice leaves and grains which showing dark spot symptoms grown in El-Dakahlia and El- Qaliubiya governorates. These fungi were isolated and identified to species level, and then screened for pathogenicity against rice plant under different treatment such as salicylic acid and hydrogen peroxide spraying and effect of these treatment on gene expression level of rice plant.
Briefly, the results can be summarized in the following points:
1- Isolation of antagonists and pathogens:
-Thirty five fungal isolates belonging to 12 genera of filamentous (mould) fungi and 4 genera of yeast were obtained from the rhizosphere soil of rice plants of El- Dakahlia and El-Qaliubiya governorates. Fusarium and Aspergillus were the most dominant isolates (520 and 410 CFU/g respectively) while Monodictys and Phaeodactylium the lowest ones (10 CFU/g for each one).
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- Eight species of rice plant pathogen belonging to 4 genera were isolated from the naturally infected leaves and grains of rice plants from El-Dakahlia and El-Qaliubiya governorates with dark spots symptoms on PDA medium where 8 species identified as Alt. betroselini, Alt. cinerariae, D.rostrata, D.spicifera, F.graminearum, F. merismoides, F. sporotrichioides and Pyricularia sp. Drechslera spicifera shows the highest percentage frequency (56 % and 53.33%) isolated from infected rice leaves and grains of El-Dakahlia and El-Qaliubiya, respectively. Drechslera rostrata follow Drechslera spicifera by percentage frequency of 33% and 26.66% isolated from infected rice leaves and grains of El-Dakahlia and El-Qaliubiya, respectively. Other species isolated from infected rice leaves and grains of El-Dakahlia and El-Qaliubiya were with low percentage frequency than two Drechslera species.
2- In vitro screening antagonism test:
- Out of 35 rhizosphere isolates, fourteen isolates showed antagonistic activity against the pathogenic fungi and were identified as. Aspergillus terrus, Aspergillus parasiticus, Aspergillus aculaetus, Penicillium dimorphosporum , Penicillium digitatum, Cladosporium cladosporiodes ,
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Aspergillus flavipes, Monodictys castaneae, Gliomastix cerealis, Rhodotorula mucilaginosa, Aspergillus candidus, Penicillium decumbens and Cladosporium state of venturia. Penicillium decumbens has the higest antagonism against Drechslera spicifera from the all other antagonists (83.9%) and Aspergillus terrus against Drechslera rostrata (82.3%).
3- Pathogenicity tests:
- Spraying of hydrogen peroxide (10mM) on leaves at third stage of growing rice plant increasing of shoot system length, leaves length and decreasing in chlorophyll content than rice plant sprayed with salicylic and untreated plant
- Drechslera spicifera was tested for pathogenicity under different treatment as salicylic acid and hydrogen peroxide spraying with Drechslera spicifera only and with Drechslera plus it’s selected antagonist (Penicillium decumbens). Result showed that spraying of salicylic acid decrease percentages of disease incidence (DI), disease severity index (DSI) in both treatment (pathogen and pathogen with antagonist). Disease incidence (DI) and disease severity index (DSI) decreased from (77.3 to 64%) and (65 to 25%) respectively in treatment of pathogen but in treatment pathogen with antagonist were disease incidence
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(DI) and disease severity index (DSI) from (64 to 55.3%) and (35 to10 %) respectively.
- Hydrogen peroxide spraying increase percentages of disease incidence (DI), but decrease disease severity index (DSI) in both treatment (pathogen and pathogen with antagonist). Disease incidence (DI) increase from 77.3 to 81% and disease severity index (DSI) decrease from 65 to 45% in treatment of pathogen but in treatment pathogen with antagonist were disease incidence (DI) increase from 64 to 79.6% and disease severity index (DSI) decrease from 35 to 15%.
4- Effect of different treatment on β -1-3glucanase expression
- The expression levels of genes encoding β -1,3-glucanase 1 (Gns1) after 48 hours reached the highest level 32-folds in the rice plant post treated with Salicylic acid followed by infestation with Drechslera spicifera (D) compared to 9.7-folds and 17.76-folds in the post treated rice plants with salicylic acid (SA) and rice plants with salicylic acid(SA) plus Drechslera spicifera (D) plus Penicillium decumbens (P) (SA+D+P) respectively. While, the expression level of Gns1 was around 5-folds in the other treatments.
- The expression levels of genes encoding β-1,3-glucanase 5 (Gns5) reached the highest expression level 77.17-folds, 48
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hours post treatment with (SA+D+P) compared to 31.77-folds in the plants post treated with (SA+D). However, the expression level of β -1,3-glucanase 5 (Gns5) was 15.5-folds, 72 hours post treatment with (SA+D) compared to 3.5-folds and 2.41-folds in the post treated rice plants with (SA) and (SA+D+P) respectively. Seventy two hours post treatment with H2O2, (H2O2+D), and (H2O2+D+P), the expression level of β-1,3-glucanase 5 (Gns5) was 0.8-fold, 6.06-folds and 1.7-folds respectively .
- After 72 hours treatment, expression level of β-1,3-glucanase 1 (Gns1) in the treated rice plants with water (Control) was 0-fold, but the expression increased to 3.4-folds in the treated plants with (D) Expression level of β-1,3- glucanase 1 (Gns1) went down to 1.5-folds in the treated rice plants with (D+P). However, the expression level of increased to the highest level 36-folds in the treated rice plants with salicylic acid, β-1,3-glucanase 1 (Gns1) dropped to 10.13-folds in the treated plants with (SA+D), and went down again to 7.6-folds in the treated plants with (SA+D+P). The expression level of β-1,3-glucanase 1 (Gns1) in the treated rice H2O2, H2O2+D and H2O2+D+P was 6.2-folds, 4.05-folds and 2.5-folds respectively