الفهرس 
NTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Evaluation of arbuscular mycorrhizal effectiveness was one of the study’s goals. fungus (Glomus fasciculatum) and potassium silicon treatments at different concentrations as eco-friendly approaches to control root-rot disease caused by R. solani and their improvement measures on disease severity percentages and vegetative growth parameters of sweet pepper plants, and include biochemical defense systems and anatomical changes to reduce the infection by R. solani.
The main findings of the present work can be summarized as follows:
1- The samples were collected from different sweet pepper fields in Nubaria city (El-Behera) and El-Sadat city (El-Menoufia) governorates.
2- Separation pathways from the infected stem and root tissues of sweet pepper seedlings showing damping-off and root-rot symptoms, on PDA medium, yielded four Rhizoctonia solani (Rs) isolates.
3- Identification of R. solani (Rs) the analysis of fungal isolates was done based on their morphological and microscopical properties. Hyphal width of Rs ranged from 4.6 μm to 6.5 μm. Maximum hyphal width was detected in isolate Rs12, whereas the minimal one was observed in isolate Rs11 which recorded (4.6 μm), while the abundant fungal growth was observed for Rs12 isolate with colony diameter of 8.9 cm, after 72 hours.
4- Pathogenicity assays revealed that all of the Rs isolates tested were pathogenic to sweet pepper (cv.702) and caused varied damping-off symptoms according to the isolate. The isolate (Rs12) recorded the highest disease severity percentage (87.5%) and the lowest percentage of 41.7 % was noted with isolate Rh7.
5- Means of sweet pepper vegetative characteristics revealed significant variation among the five tested control treatments within all the studied characteristics:
a- The most best significant shoot and root fresh weights were recorded with control treatment and the lowest values for both characteristics resulted from Rs12 infection treatment.
b- The tallest significant shoot length was recorded in case of the control treatment (free of Rs infection), while the infection with Rs12 resulted in the shortest significant shoot length, with a reduction amounting to 42 % compared to the control treatment.
c- The response of the total numbers of flowers/plant to Rs isolates infection followed an opposite direction. The least significant number of flowers produced with the control treatment (5 flowers/plant), however, the infection with Rs9 resulted in the highest significant number of flowers (8.7 flowers/plant).
d- Concerning the root and shoot dry weights, the control treatment resulted in the highest significant values for both characteristics, while the infection with Rs12 resulted in the lowest significant root dry weight and no significant difference was detected among all the investigated Rs isolates concerning the shoot dry weight.
6- In vitro results of potassium silicate (PSi) treatments against Rs12 growth at concentrations of 12, 16, 18, 20 ml/L showing significant Rs inhibition percentages of mycelial growth on PDA medium, where liner growth was reduced by 100 % at 16-20 ml/L PSi. While 12 ml/L PSi showed reduction of 38.7 %. No inhibition was observed below 12 ml/L PSi treatment.
7- Scanning Electron Microscope (SEM) observations showed that PSi treatments have strong effects on hyphal morphology of Rs12 isolate including:
a- Sparse and asymmetric mycelium, also curling, twisting, and wizened with distorted hyphae, swollen cells, and cupped inflated (at the brim).
b- Newly developed hyphae possessed rough surfaces, were thinner, and were deformed.
c- Hyphae were enlarged and expanded at the brim, whereas mycelium became blasted, wizened, and cupped In comparison to untreated mycelia of Rs12 cultures, which showed that, in contrast, long, even, and round hyphae.
8- In vivo results of infection factor (infected and non-infected) exerted a significant effect on sweet pepper growth parameters. where PSi treatments, as well as, AMF caused the positive significant effect on sweet pepper growth parameters. Whereas, the trend of all experimental results indicated that 20 ml/L PSi and 16 ml/L PSi treatments improved all vegetative characteristics with a low significant difference between them. Moreover, the co-treatment (AMF+ 12 ml/L PSi with Rs12) stimulated the effective both of AMF or 12 ml/L PSi alone among all growth parameters that have been studied.
9- Disease severity percentage (DSi) was decreased with all tested treatments.
a- In the case of 20 ml/PSi, DSi was reduced by 66.7 % in the 1st season, while, in the 2nd season, it was reduced by 80.5%. In addition, 16 ml/PSi treatment decreased DSi by about 58.4 and 65.5 % in both seasons, respectively. Moreover, 12 ml/L PSi had the lowest effectiveness of disease severity with 50 decrease %.
b- In the case of the AMF application, the DSi diminished about 66 %.
c- Addition of (12ml/L PSi to AMF) improved the diminished of disease severity from 36.7 to 30 % compared to the control treatment infection with Rs12.
10- The AMF colonization, in pepper roots, was 53 % in 1st season, while 68.3% in 2nd season. Moreover, the interaction treatment of (AMF+ 12 ml/L PSi with Rs12) resulted in 61.7 %, after 45 days of planting.
11- The positive significant effect of PSi and AMF treatments on sweet pepper growth parameters could be summarized as follows:
a- In 1st season the total fresh weight increased to 53, 117 and 106 % for the application of 16, 20 ml/L PSi and AMF, respectively. While 34 % increase in shoot length due to 20 ml/L PSi. Total dry weight increased amounted to 95.6, 123.8 and 119.8 % for the application of 16, 20 ml/L PSi and AMF treatments, respectively. Moreover, the highest significant number of flowers was recorded in case of 20 ml/L PSi treatment.
b- In 2nd season, also 20 ml/L PSi recorded the highest value of total fresh and dry weights, 38g and 6.78 g, respectively. As well as the number of flowers with up to 54.3 flower/plant.
c- The interaction treatment (12 ml/L PSi+ AMF) against Rs12 stimulated the effective of AMF or 12 ml/L PSi alone among all growth parameters.
12- All the tested treatments leading to a significant increase in the chlorophyll content under investigation, where the highest level was recorded with 20 ml/L PSi treatment which reaching an average of 74.63 SPAD, while the co-treatment of 12 ml/L PSi +AMF and R. solani showed 56 % increasing of chlorophyll content compared to the infected control.
13- The highest accumulation of total phenol compounds (TPC) was recorded after day 7 post-inoculation in case of 16 ml/L PSi (181 mg g−1) followed by the other two tested doses of PSi and AMF, which are not statistically different. Also, application of the combination treatment of (PSi+ AMF and Rs12) increased the effectiveness of both treatments of 12 ml/L PSi or AMF alone, where the highest values recorded reached 227.92 mg g−1 at the 3rd day for TPC, compared with the untreated, non-infected sweet pepper.
14- Peroxidase activity (POX) noticed the highest significant increased at 14 days after infection with R. solani due to 20 ml/L and 16 ml/L PSi amounting to 60.37 and 57.05 µmol min-1 mg-1 protein of POX, respectively. While, the combination treatment of (AMF and 12 ml/L PSi and R. solani) recorded the highest significant increase of POX activity where reached 38.11 µmol min-1 mg-1 protein at the 7th day compared to both treatments of AMF and 12 ml/L PSi.
15- Catalase activity (CAT) showed the highest activity after 14 days post-inoculation by R. solani in case of AMF and 16 ml/L PSi, amounting to 50.4 and 49.8 U min-1 mg-1 protein of CAT, respectively. Seemingly, the interaction of host-pathogen-AMF increased CAT activity that may be increased the defense of plant cell.
16- Polyphenol oxidase (PPO) recorded the highest activity rate at 14 days after inoculation with R. solani. In the case of AMF application, PPO activity was stimulated with significantly increase amounting to 10.97, while 20 ml/L PSi recorded increase of 9.03 (U mg-1 protein)
17- The leaf cell wall thickness in case of PSi treatment reached 98 % increased, and stem cell wall thickness increase 71 % in the co-treatment. Moreover, the thickness of xylem tracheid’s in roots were increased to 107 and 56 % in case of PSi and co-treatment, respectively.
18- Leaf cell wall width increased to 51.8 %, and stem cell wall width increased also to 26.5 % in case of co-treatment.