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Series of laboratory (in vitro) examinations were carried out to recognizethe most potent fungi isolates and optimum culture conditions helps in solubilizing sparing phosphate in soil. Therefore, the present study aimed to isolate and screening of phosphate solubilizing fungi (PSF), study the contribution of PSF on solubilization of tri-calcium phosphate through excretion of acid and alkaline phosphatase and determine the optimal conditions for phosphate solubilization. From 12 fungal isolates, only four were chosen depending on their capacity to convert tri-calcium – P into soluble one. In this regard, Aspergillus niger, Aspergillus flavus, Aspergillus ficuum and Fusarium oxysporum were efficient in producing halo zone around the colonies on petri dish. Aspergillus niger was the most efficient phosphate solubilizer on Pikovskaya’s agar plates (PVK) achieving solubilization index (PSI) 2.4, followed by Aspergillus flavus with a SI= 2.3. The perfect activities of selected fungal isolates were detected with incubation periods 7 days and temperature 30°C for maximumphosphate solubilization, acid and alkaline phosphatase activities, pH 7.0 for maximum phosphate solubilization, pH 6.0 for maximum acid phosphatase activity while pH 8.0 was suitable for maximum alkaline phosphatase activity for both A. niger and A.flavus.

Isolation trials from the rotten roots of soybean roots collected from three Egyptian governorates, i.e. Giza, Menoufia and Gharbia yielded many fungal isolates. The isolated fungi were purified and identified as Alternaria spp., Fusarium moniliforme, Fusarium oxysporum, Fusarium semitectum, Rhizoctoniasolani and unknown fungi. Laboratory, greenhouse and field studies were conducted to study the effect of two natural extracts and antioxidants in comparison with two fungicides on the reduction of damping-off and root-rot diseases. In vitro studies showed that these treatments significantly reduced the linear growth of the tested fungi compared with control treatment.Greenhouse experiment revealed that all the tested treatments significantly reduced damping-off and root-rot compared to the untreated plants. The most effective treatment was obtained by the extracts of neem and Eucalyptus followed by the antioxidants salicylic and oxalic acid, which reduced both damping-off and root-rot diseases. Crop parameters, i.e. plant height, number of branches, number of pods, seed yield / plant, weight of 100 seed as well as the average weight of seed yield (kg)/plot, were recorded at harvest. Also, total N and crude protein in the seeds were greatly increased due to the tested treatments as well as the treatment with two fungicides: Vitavax-T and Monceren.