ROLE OF ENDOPHYTIC PSEUDOMONAS AS PLANT GROWTH PROMOTERS UNDER DESERT CONDITION

Plant growth promoting endophytes enhance the plant growth using multiple metabolic activities directed and contribute to the growth, health and development of plant. A total of 46 strains isolated from the rhizosphere of maize, sorghum, barley and wheat plants were screened for their efficiency as plant growth promoting endophytes. Bacterial isolates induced the highest length and weight of maize seedlings on Hoagland media were selected for further investigations. All selected endophytic bacteria possess HCN and indole acetic acid production, while only four isolates showed phosphate dissolving activities. Using Chrome Azurol S plates revealed that all selected  isolates were positive to  siderophore production. For characterization of siderophores, ferrate hydroxamate type were detected in five bacterial isolates, ferrate catecholate type detected in only three isolates, while no carboxylate siderophores were recorded for any isolates. HPLC analysis of the highest active two isolates revealed the presence of indole acetic acid and indole butyric acid. Phylogenetic analysis of 16S rRNA sequence of the two isolates showed maximum sequence similarity with Pseudomonas aeruginosa strain PAO1 and Pseudomonas geniculata strain ATCC 19374. 
                          A field experiment was conducted at El-Qantara Sharq experimental station, Desert Research Center (DRC) for evaluation of Ps. aeruginosa and Ps. geniculata as plant growth promoting endophytes on maize. Bacterial inoculation recorded an increase in  biological yield reaching 55.2  and 33% over control for  Ps. geniculata and Ps. aeruginosa, respectively. Concerning to chemical constituent of maize grains,inoculation process significantly increased the carbohydrate and oil % with about 4.6 and 4.2% for both bacterial strains. While no change in endophytic Pseudomonads count were detected inside the root  of  treated plants comparing to control , the inoculation process have a positive effect on the activity and abundance of microbial community in the rhizospheric zone.