الفهرس 
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Abstract
Two plant species and two algae pertaining to different families were tested for their fungicidal and bactericidal activities against some of the most important pathogens. The powder of whole plants of Sesbania sesban and Cymbopogen citratus. Stapf were extracted using hexane and ethanol. The yield of extracts, after evaporation of the solvents using Rotary evaporator, were (4.2, 3.5, 4.14, 3.2 gm) of ethanol and hexane extractives of Sesbania sesban and Cymbopogen citratus, respectively. The powder of algae were extracted with ethanol and hexane with a yield of 4.4, 3.8 and 5.2, 4.4 gm extractives of ethanol and hexane of Spirulina platensis and Scenedesmus sp., respectively. After evaporation of organic solvents, all extractives were solubilized in water by using (DMSO) to test their biological activities against the tested pathogens.
Plant and algae extracts were tested for their antifungal and antibacterial activity against eight fungal pathogens, Rhizoctonia solani (Kuhn), Fusarium oxysporim (Schiech), Penicillium digitatum (Pres.) sacc., Aspergillus niger (Van&Tieghem), Rhizopus stolonifer (Ehren), Alternaria solani ((Fr.) keissler, Pythium debaryanum (Alta. Cook &Webster) and Botrytis cinerea (Sardiña). Also, the antibacterial activity of the extracts was tested against two species of bacteria: bacteria of crown gall disease A. tumefaciens (E. F. Smith and Town.) (Family: Rhizobiaceae; Class: Alpha Proteobacteria) and soft mold disease E. carotovoravar. Carotovora (Family: Enterobacteriaceae; Class: Gamma Proteobacteria) .
The toxicity of the plant extracts against fungi was evaluated by comparing their EC50 values. All tested extracts showed increase inhibition with increasing concentration. Among the plant extracts screened, it was found that ethanol extract of S. sesban plant showed maximum antifungal activity against A. solani and A. niger fungi with EC50 values of 0.011 and 0.135 mg/L, respectively. Higher inhibitory activity was recorded against tested fungi by using hexane extract of S. sesban especially against P.debaryanum and F. oxysporium fungi with EC50 values of 0.0031 and 2.008 mg/L, respectively. While hexane extract of C. citratus showed less inhibitory effect against tested fungi.
Also, the toxicity of the algae extracts against the tested fungi was evaluated by comparing their EC50 values. All tested extracts showed increase inhibition with increasing concentration. It was found that ethanol extract of S. platensis recorded the highest inhibitory effect against P. debaryanum and F. oxysporum with EC50 values of 10.59 and 16.75 mg/L, respectively.
The ethanol extract of plants and algae showed the highest antifungal activity compared with hexane extract, so the ethanol extract of plants and algae were screened for their antibacterial activity.
Result of the antibacterial activity, expressed as minimum inhibitory concentration (MIC), of the ethanol extracts of the two plants, Cymbopogen citratus and Sesbania sesban and the two algae, Scendesmus sp. and Spirulina platensis against Agrobacterium tumefaciens and Erwinia carotovora showed that the ethanol extract of Scendesmus sp. alga had the highest inhibitory effect against Erwinia carotovora with MIC value of 2500 mg/L. In contrast, Spirulina platensis extract was the least effective extract followed by Cymbopogen citratus and Sesbania sesban.
The preliminary phytochemical investigation of the tested plants and algae revealed the presence of triterpenes and flavonoids C. citratus, S. sesban plants and S. platensis and Scendesmus sp. algae. In addition, S. sesban plant and S. platensis alga contain glycosides in contrast with C. citratus plant and Scendesmus sp. alga which were free of glycosides. Alkaloids were found in all plants and algae except S. platensis.
Fractionation of crude ethanol extract of S. platensis was carried out with column chromatography employing a step gradient solvent system from low to high polarity. The resulting fractions were pooled to five main fractions (3.20, 4.15, 3.4, 3.62, 5.1 gm ). On the other hand, the ethanol extract of S. sesban was subjected to silica gel column chromatography in chloroform and using chloroform / methanol solvent system. The resulting fractions were pooled to two main fractions (5.3, 7.6 gm ).
Crude ethanolic extracts of S. platensis alga and S. sesban plant, the most promising antifungal extract were fractionated on column chromatography as described in materials and methods. Obtained fractions and carbendazim exhibited broad spectral antifungal activity against: Soil born fungi: (R. solani, F. oxysporum and B.cinerea) and Post-harvest fungi: (R. stolonifer).It can be concluded that the hexane : ethylacetate (1:3) fraction of S. platensis was the most active as fungicide against all of the tested fungi. On the other hand, it was found that the chloroform fraction of S. sesban was the most effective fraction as fungicide. Considering the sensitivity of the microorganisms, it was noticed that F. oxysporum was more sensitive to these fractions followed by B. cinerea then R. solani and R. stolonifer, respectively. Also results revealed that all of the tested fractions showed more antifungal activity than the crude extract and showed less antifungal effects than the reference fungicide, carbendazim.
GC-MS analysis of hexane:ethylacetate (1:3) fraction resulted from fractionation of crude ethanolic extract of S. platensis revealed the presence of forty (40) peaks indicating the presence of forty compounds. The spectra of the compounds were matched with NIST and Willey library. Their structures were identified by the percentage similarity values. They confirmed by the study of classical fragmentation pattern, base peak and molecular ion peaks of the compounds. The major compounds were found to be Dodecane with peak area of (7.35 %), n-Hexadecanoic acid (14.83 %) , Hexadecanoic acid, ethyl ester (9.43%) , Phytol (5.94%) , 9,12-Octadecadienoyl chloride, (Z,Z)- (3.38%) and D-Homo-24-nor-17-oxachola-20,22-diene-3,7,16-trione, 14,15:21,23-diepoxy-4,4,8-trimethyl-,(5à,13à,14á,15á,17aà)- (8.45% ).
GC-MS analysis of chloroform fraction of ethanol extractives of S. sesban clearly showed the presence of forty components. The chemical properties of the major components isolated from the ethanolic fraction were 3,7,11,15-Tetramethyl-2-hexadecen-1-ol with peak area of (3.34%), n-Hexadecanoic acid (7.91%), Hexadecanoic acid, ethyl ester (12.06%), 9,12,15-Octadecatrienoic acid, (Z,Z,Z)- (11.91%) and 9,12,15-Octadecatrienoic acid, ethyl ester, (Z,Z,Z)- (30.34%).
The effect of the most fungitoxic compounds of S. sesban plant and S. platensis alga on growth of Aspergillus flavus and aflatoxin production was determined. It was found that the ethanol extract of Sesbania sesban plant was effective more than the ethanol extract of Spirulina platensis alga against A. flavus. The aflatoxins were determined in sterilized corn which inoculated the spore suspension and treated with EC50 of the synthetic fungicide (carbendazim) and a series of concentrations of the ethanol extract of Sesbania sesban (100,300,500,700 and 1000 mg/l).
Results revealed that aflatoxin B1 is absent in all concentration and also in control. Aflatoxin B2 produced by A. flavus on all concentration except 1000 mg/land control. Concentration 1000 mg/l of Sesbsnia sesban revealed the highest reduction in the production of aflatoxins with aflatoxin G2 concentration of 9.595×10-5µg /g.
The most fungitoxic fractions of the strongly fungitoxic plant and algal extracts were formulated to test their effect on corn seedlings in comparison with the corn plants infected and uninfected with F. oxysporum. Results revealed that:
1- The infection with F. oxysporum decreased the length of both shoot and root systems of corn plants than the uninfected ones.
2- The formulated fraction of Sesbania sesban decreased the length of root system than the formulated fraction of Spirulina platensis.
3- The infection with F. oxysporum increased the leaf fresh weight and decreased the leaf dry weight of corn plants than the uninfected plants. Treatments with concentrations of 1000 mg/l of Spirulina platensis fraction increased the leaf fresh weight than that of uninfected corn plants.
4- All of the concentration of S. sesban fraction decreased the fresh weight of corn leaves, and affect slightly the dried weight of leaves.
5- The level of Chlorophyll a, Chlorophyll b and total Chlorophyll increased in the treatments of 1500 and 5000 mg/l of Spirulina platensis fraction.
6- At lower concentrations of 1000, 2000 and 3000 mg/l the level of all types of Chlorophyll was lower than that of uninfected corn plants. On contrary, the highest concentration (5000 mg/l), caused significant increase in the level of all types of Chlorophyll than these of uninfected corn plants.