الفهرس 
ACKNOWLEDGMENT
Control of soybean charcoal rot disease by using bioagents and silicon:Only 14 pages are availabe for public view
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Abstract
Charcoal rot disease of soybean caused by the fungus M.phaseolina (Tassi) Goidanich, is the most common disease of soybean.Macrophominaphaseolina invades the roots of a host at an early stage, 1–2 weeks after planting, but the symptoms appear only in mature plants. Annual losses in soybean with charcoal rot averaged 5%, but sometimes reached 30 to 50%. The present study aimed to control the disease by untraditional methods such as biocontrol agents, application of silicon compounds to the soil with irrigation water individually and in combination with bioagents. The results of this study could be summarized as follows:
1- Twenty six isolates were isolated from roots, stems and leaves of infected soybean plants, showing symptoms of charcoal rot collected from different counties of AssiutGovernorate. All isolates were identified as M.phaseolina (Tassi) Goidanich.
2- All isolates were able to infect soybean (Giza 111cv.) causing charcoal rot with different degrees of severity. The highly pathogenic isolates were isolates No. 2, 5, 19 and 20.
3- Pathogenic isolate No. 5 was identified as M. phaseolina by using morphological characters and PCR-sequence.
4- All tested bioagents (fungal and bacterial) isolates were able to inhibit the mycelia growth of M.phaseolina with variation in their antagonistic capabilities. The highest inhibition of pathogen growth caused by T. asperellum (1) No.6,T. longibrachiatum (2) No.9,P. aeruginosa (B1) and B. vesicularis(B2).
5- Silicon compounds (Sodium silicate and potassium silicate) reduced the mycelial growth of tested isolate of the M. phaseolina. The growth inhibition increased with increasing in silicon concentrations.Generally,sodium andpotassium silicate caused the same effect on mycelial growth of M. phaseolina.
6- Under greenhouse conditions, fungal bioagents significantly reduced the charcoal rot severity compared to infected control.Treatments with T. longibrachiatum or T. asperellumreduced disease severity percentage from 82% in control to 42 and 43% respectively.Treatments containingbioagentsindinidually or in combination with silicon gave the highest increment percentage of growth parameters (root fresh weight, root dry weight, shoot fresh weight and shoot dry weight). Treatments with B. vesicularis, and (P. aeruginosa + Silicon) gave the highest percentage of growth parameters.
7- (Trichodermaasperellum + S) and (T. longibrachiatum + S) gave the highest reduction of charcoal rot disease and reduced disease severity. Addition of T. asperellumand T.longibrachiatum, separately to infested soil with pathogen isolate caused the highest increase in yield than other treatment, followed by treatments containing bacterial bioagentsP. aeruginosa and B. vesicularis, respectively.
8- Application of (T1 + S), P. aeruginosa and T. longibrachiatum showed significant differences in total phenol contents for all treatments compared to untreated plants, after eight days from application significant increases in total phenol.
9- Salicylic acid amount was significantly increased more rapidly by application of B. vesicularisand silicon, after two days to the eighty day fromapplication.
10- The highest Peroxidase activity was observed when treated by P. aeruginosaand (T1 + S) after eight days from application. The different application showed significantly increasing in peroxidase activity after eight days from application.
11- The highest Phenylalanine ammonia-lyase activity was detected in treatments with(T1 + S) followed by B. vesicularis(B2) and T. asperellum (T1).
12-The highest Polyphenoloxidase activity was observed when soybean plants treated by T. asperellumand P. aeruginosa. After eight days from application, the diseased soybean plant samples showed significant differences in Polyphenoloxidase activity for all tested treatments compared to the untreated plants.
13- Trichodermalongibrachiatumexhibited higher increasing in catalase activity in host plant, followed by T. asperellum and P. aeruginosa.
14- The highest value in lipoxigenase activity was detected by P. aeruginosa application followed by T. longibrachiatum and (T2 + S). The (B1 + S) application was the lowest in lipoxigenase activity.
15- In-vitrostudies, bioagents (T. longibrachiatumand P. aeruginosa) showed substantial amounts of siderophore production.
16- Trichodermalongibrachiatumand P. aeruginosa showedhigher ability to dissolve phosphate. While, isolate T. asperellum showed the highest ability to dissolve zinc followed by P. aeruginosa.
17- In-vitro, B. vesicularis showed high ability to produce Lysis enzymes.
18- All bioagents, fungalisolates (T. asperellum and T.longibrachiatum)and bacterial isolates (P. aeruginosa and B. vesicularis)showed activity against M. phaseolina mycelium by using scanning electron microscope.
19-Soybean plants treated with sodium silicate showed significantly increased in anatomical structures of root, stem, and leafe such as; root, stem diameter, number & diameter of the vascular bundles and thickness of cortex and pith com compared with untreated plants.