Abstract
Seven endophytic actinobacterial isolates were isolated from wheat roots, which collected from the middle area of Riyadh at Saudi Arabia. The obtained results revealed that, all endophytic isolates have the ability to produce the growth hormone indole acetic acid (18.2 - 30.7 mu ml(-1)). In vitro antifungal activity of the seven endophytes was investigated against the phytopathogenic fungus Fusarium graminearum. Out of these, the isolate Endo-1 showed the maximum fungal inhibition. The optimum cultural conditions were studied to obtain the highest in vitro antifungal activity of Endo-1 isolate. It was found that the first incubation day, pH 5.5, incubation temperature 30 degrees C, starch as the best original carbon source, and peptone as the best substitutive nitrogen source were the best conditions for maximum inhibitory effect. On the other hand, Endo-1 isolate was tested under greenhouse conditions to determine its efficacy in the biocontrol of Fusarium head blight disease of wheat. The data showed that treatment with Endo-1 isolate significantly reduced both disease severity and incidence and improved all assessed growth parameters when compared with the control treatment. Endo-1 isolate was identified as Streptomyces olivaceiscleroticus using the morphological, physiological and biochemical characteristics and the identification was confirmed molecularly using 16S rRNA. Thus this endophytic isolate has the potential as plant growth promoters as well as a bio-control agent, which is a useful trait for crop production in nutrient deficient soils.