Isolation and Assessment of Nitrogen-Fixing Bacteria from Arundo Donax L. (Giant Reed) for Use As Biofertilizers.

Arundo donax, giant reed, is a perennial grass that has been extensively evaluated as a source for biofuel. Interestingly, in temperate climate zones Arundo grows very quickly each year, reaching 4-6 m without any fertilization. This rapid growth without fertilizer suggests a possible involvement of biofertilizers. The objective of this project was to isolate and characterize nitrogen-fixing (N-fixing) bacteria from rhizosphere soil and endophytically from inside roots and stems of Arundo. Isolations for N-fixing bacteria were made using different N-free medium. Results showed that 131 of putative nitrogen-fixing bacteria were isolated from rhizosphere soil, endophytically from inside roots and stems. The nitrogenase activity of the putative N-fixing bacteria was confirmed using acetylene reduction assay. Other PGP traits such as IAA production, phosphate solubilization, and siderophore production were evaluated in vitro. DNA was extracted and 16S rDNA sequence was used for molecular identification. Selected N-fixing strains were tested on corn and wheat as microbial inoculants under greenhouse condition. Interestingly, the results showed that the selected N-fixing bacteria can promote corn and wheat growth by increasing the nutrient uptake rate, root dry weight and the root morphology parameters such as total root length, root volume, number of tips, fine roots and root surface area.