الفهرس 
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Abstract
Endophytic fungi inhabit the internal plant tissues forming a mutualistic relationship with their host plant and penetrate their host without estimating its defense mechanism to achieve ”stable symbiosis”. They may enhance the growth of their host, and help it to adapt environmental stresses and resist invading by pathogens, insects or weeds. They also produce many valuable secondary metabolites that can be applied in many fields. Pelargonium graveolens (geranium) is one of the medicinal plants grown in Egypt. The plant and its oil (geranium oil) have antioxidant and antimicrobial activity against many pathogens. This study characterizes the P. graveolens- associated endophytic fungi from Beni-Suef, Egypt and investigates their impact on the host plant.
A total 20 morphologically different fungal species were isolated from P. graveolens and identified by combining the morphological and molecular methods. Also, antifungal activity against Rhizoctonia solani, Sclerotium rolfsii, Fusarium solani and Microsporum audouinii was tested. Three endophytic fungi (Emericella nidulans (E6658), Penicillium sp. (E6651) and Aspergillus niger (E6657)) that showed high antifungal activity were selected for inoculation of P. graveolens, under stressful and non-stressful conditions, in a pot experiment. Morphological and physiological parameters of the inoculated and non-inoculated plants were estimated under stressful and non-stressful conditions.
Results showed that, P. graveolens is extensively colonized by fungi. The root exhibited the highest colonization frequency CF% and isolation rate IR% (96% and 99% respectively). Phylogenetic analysis showed that, they are relatively related genetically. The most occurring genera were Aspergillus and its teleomorph Emericella (CF=28%). Most of the isolates exhibited an antifungal activity against one or more of the tested pathogens, while Aspergillus niger (E6657) and Penicillium sp. (E6651) showed a very strong activity against all the tested pathogenic fungi. The maximum inhibition rate for Emericella nidulans (E6658) against Microsporum audouinii was 80%. Aspergillus niger (E6657) and Penicillium sp. (E6651) enhanced the growth of P. graveolens over
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the non-inoculated ones and alleviated the harmful effect of cadmium stress on its biomass. They also improved the antioxidant defenses of their host under the investigated stresses, particularly cadmium one. This improvement was linked with a stimulation of phenylalanine ammonia-lyase (PAL) and antioxidant activity, increasing flavonoids content, while lessening hydrogen peroxide (H2O2) and lipid peroxidation.