الفهرس 
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Abstract
The use of inexpensive, ecologically sound and environmentally friendly microbial fertilizers is a new strategy to solve the problem of soil infertility and plant productivity. The biological conversion of insoluble phosphorus (P) to soluble and available forms is one of the better choices for enhancing crop production by supplying essential nutrients to plants.
The thesis aimed to investigate the physiological and biological characteristics of some isolates of phosphate solubilizing fungi and their effect on seed germination and growth improvement of Vicia faba. A total of 137 fungal isolates were isolated and identified from 30 soil samples collected from from different localities and habitats in Beni-suef governorate. Soil samples were taken from rhizospheres of Alhagi graecorum Boiss., Allium cepa L., Ehrharta calycina Sm., Ludwigia stolonifera (Guill. & Perr.) Raven, Mentha longifolia L., Phragmites communis Trin., Triticum aestivum L. and Zea mays L. Twenty-three fungal isolates were tested to solubilize tricalcium phosphate in Pikovskaya,s broth medium and the relationship between solubilization activity of these isolates and PH of the medium was also determined. Nine isolates were molecularly identified to genus level by multi loci DNA barcoding using internal transcribed spacer1and 2 (ITS1 and ITS 2) of the rRNA gene cluster. Blasting analysis of ITS1 and ITS 2 sequences revealed that five isolates belonged to Aspergillus and four isolates belonged to Penicillium. Calmodulin (CaM) and beta- -tubulin(BenA) gene markers were used to identified the nine isolates to species level. The antagonistic potential of these isolates was also detected against some phytopathogenic fungi ( Alternaria alternata, Fusarium solani, Geotrichum candidum, Rhizoctonia solani and Sclerotium rolfsii. The highest inhibition percentage (70%) against Alternaria alternata was recorded by Aspergillus japonicus 2. The organic acid production of eight fungal isolates was detected by using high performance liquid chromatography (HPLC) technique. Seven organic acids were detected (salicylic, ascorbic, citric, formic, lactic, oxalic, and malic acids). The effects of carbon, nitrogen, pH values and time on phosphate solubilization by Aspergillus japonicus 2 were studied. The highest phosphate solubilization by Aspergillus japonicus 2 was obtained by using sucrose as a carbon source and also ammonium chloride and tryptophan as a nitrogen source. The pH value that gave the highest solubilization percentage (90%) by Aspergillus japonicus was 3. After eight days of incubation of Aspergillus japonicus 2, the solubilization percentage reached its maximum value (80.2%). The growth improvement of Vicia faba could be achieved by soil inoculation of phosphate solubilizing fungi (Trichoderma harzianum or Aspergillus japonicus)
Keywords: Aspergillus japonicus, Phosphate solubilizing fungi, Trichoderma harzianum, Vicia faba, Biocontrol.