Abstract

Several strains were isolated from rhizosphere of wheat in Eastern Algeria. All the 10strains (Azo4, Azo5, Azo6, Azo7, Azo8, Azo10, S1, S2, S3 and S9) were identified; based also on the characteristics which are not only morphological, characteristics such as shape but physiological ones: optimal temperature, pH optimum and NaCl tolerance. These isolates were screened in vitro for their growth promoting traits like production of indole acetic acid (IAA), ammonia (NH₃) and solubilize phosphate. The bacterial strains have an optimum growth pH equal to 6.8; in a broad temperature range (28 and 37°C). The molecular identification was done by simple PCR to amplification for 16S rDNA gene using primers AZ16S-D. Some strains (Azo4, Azo5, Azo6, Azo7, Azo8 and Azo10) have high identity with genus Azospirillum which indicates that these isolates belong to theAzospirillum genus, specially to species of Azospirillum brasilense A nested PCR approach performed with degenerate primers was used to amplify nifH gene fragments from the bulk DNA. The amplification product bands at the expected nifH gene fragment size are about 370 bp. Some isolates (S1, S2, S3, Azo4, Azo5, Azo6, S9 and Azo10) were considered by the nitrogen-fixing gene nifH detection of their genome. We managed to highlight the contribution between A. brasilense and durum wheat with inoculation experiments performed under greenhouse conditions showed that all A. brasilense (six strains) have a good report for growth of roots and plants and improve the production of durum wheat (Triticum durum var: GTA). These data demonstrate the importance of the test especially in programs to improve the quality of wheat in Algeria.

Key words: Rhizobacteria, indole acetic acid, ammonia, 16S rDNA, Azospirillum brasilense, nifH.

Abbreviation

PGPR, Plant growth promoting rhizobacteria, PCR, polymerase chain reaction, LB, medium Luria bertani; bp, base pairs; IAA, indole-3-acetic acid.