الفهرس 
I) IntroductionOnly 14 pages are availabe for public view
Abstract
Curvularia species are among most common fungal pathogens of rice, causing leaf spot diseases. Infection with Curvularia species causes quantitative along with qualitative damage on small grains and rice plants. The aim of this study was to assess the potential of volatile metabolites and nonvolatile compounds from thirty fungal isolate belonging to 12 genera of filamentous mould fungi which previously isolated from rice rhizosphere soil of El- Dakahlia and El- Qaliubiya governorates in Egypt during summer 2014.
In vitro studies have demonstrated that out of thirty fungal isolate, 7 isolates consistently produced antifungal volatiles which inhibited mycelial growth of Curvularia spicifera in comparison with control plate. The volatile metabolites produced by the Fusarium moniliforme var subglutinans displayed the highest significant inhibitory effects on Curvularia spicifera growth with inhibition percentage (45%) followed by Fusarium fusarioides, Penicillium verrucosum and Aspergillus terreus with inhibition percentage (32%, 26.1% and 25.3%) respectively. The chemical composition of total compounds produced by fungus Fusarium moniliforme headspace sample using gas chromatography mass spectrometry analysis (GC-MS) predictable nearly 15 compounds out of them 7 volatile compound which identified as acetaldehyde, oxirane, ethanol, ketene, acetaldehyde cation, ketene cation and ethoxide of acetate.
While the chemical composition of the total headspace sample organic compounds produced by fungus Penicillium verrucosum and Aspergillus terreus using gas chromatography mass spectrometry analysis (GC-MS) revealed nearly 15 and 12 compounds respectively but only the volatile compounds with low m/z ratio produced from Penicillium verrucosum revealed 6 compound which identified as acetaldehyde, ethanol, ethoxide of acetate, ketene, butanal and 2-methylpropanal and also, Aspergillus terreus revealed 6 volatile compounds emitted which identified as acetaldehyde, ethanol, butanal, ethoxide of acetate, ketene and 2-methylpropanal. The major common compound was acetaldehyde which emitted with the highest intensity (8178410) in head space sample of F. moniliforme var subglutinans but in the lowest intensity (39662) in case of Aspergillus terreus head space sample.
On the other hand, mycelial growth of target pathogen (Curvularia spicifera) was retarded by non-volatile metabolites from four fungal species of 30 rice rhizosphere fungi isolated against brown spot pathogen. The brown spot pathogen (Curvularia spicifera) growth was highly significant restricted at performed ethyl acetate crude extract of Aspergillus terreus (2.1 cm) followed by followed by Penicillium verrucosum (1.9 cm) then, Aspergillus fumigatus (1.4 cm) while the metabolite of Penicillium dimorphosporum showed lowest activity (1.1 cm).
The metabolites were characterized and identified by Gas-Chromatography Mass-Spectrophotometry (GC-MS) analysis. Compounds methyl 2-hydroxy-5-(1H-indol-3-yl)-4-methyl-3-methylenecyclopenta-1,4-diene-1-carboxylate (1), methyl2-hydroxy-5-(1H-indol-3-yl)-3-methylene-4-oxocyclopent-1-ene-1-carboxylate (2), methyl(4R,7R)-3-hydroxy-8,8-dimethyl-octahydro-1H-4,7-ethanoindene-5-carboxylate (3), methyl (4S,7S)-8,8-dimethyl-3-oxo-2,3,4,5,6,7-hexahydro-1H-4,7ethano indene-5-carboxylate (4), (4R,7R)-5,5 dimethyloctahydro-1H-4,7-ethanoinden-1-one (5) and anthraquinone (6) were the main components produced and purified from Aspergillus terreus ethyl acetate crude extract but compounds indolin-3-ol (13), 3,4-dihydroquinolin-3-ol (14), 4-phenylquinoline (15), 4-phenyl-3,4-dihydroquinoline (16), 3-phenyl-2H-oxeto[2,3-b]quinolin-2a(3H)-ol (17) and 3-ethyl-4’-phenyl-1’,4’-dihydro-2’H-spiro[oxirane-2,3’-quinolin]-2’-one (18) revealed at high m/z ratio constituents of Penicillium verrucosum ethyl acetate crude extract. Quantum chemical calculation via density functional theory (DFT) can be studied the optimized structure and determine the active site of these nonvolatile compounds. Compound methyl (4S,7S)-8,8-dimethyl-3-oxo-2,3,4,5,6,7-hexahydro-1H-4,7ethano indene-5-carboxylate (4) and (4R,7R)-5,5 dimethyloctahydro-1H-4,7-ethanoinden-1-one (5) were the most significant effective purified antimicrobial compounds against Curvularia spicifera purified from Aspergillus terreus ethyl acetate crude extract.