Résumé:
The plant growth promoting rhizobacteria (PGPR) are commonly inoculated to
improve growth and yield of agricultural crops. They are developed to be effective plant
growth promoting and successful bioconrtol agents by diverse set of traits. The present study
focuses on screening of PGPR isolates showing biocontrol to phytopathogenic fungi and
promotion of plants growth. 109 strains belonging to Pseudomonas and Bacillus genera have
been isolated from rhizosphere and endosphere of tomato roots from Mostaganem region.
Among which, 46.79% have been isolated from ectorhizospheric region, 35.78% isolated
from the rhizoplane and 17.43% from the endorhizosphere. They were screened initially via
their in vitro antagonistic activity against F. oxysporum f. sp lycopersici by dual culture
inoculation on plate assay. 54.12% of the tested isolates demonstrated a variable inhibition
rate of the phytopathogenic agent growth. The production ability of volatiles substances
(HCN), siderophores and hydrolytic enzymes (pectinase, CMcellulase, protease and amylase)
has also been detected.
These isolates were then tested in vitro for specific PGPR traits such as the production
of phosphate solubilizing enzymes, Indole Acetic Acid (IAA) and ammonia. Among the
tested strains, 41% were able to solubilize the inorganic P, 69% were able to produce AIA and
the all isolates were ammonia producers.
Inoculation of tomato seedlings with seven different isolates has significantly
enhanced seed germination, seedling vigor index, plant height, fresh weight and dry weight in
comparison with control. Biocontrol activity of the seven (07) bacterial isolates has been also
evaluated under greenhouse conditions. The results indicated that these Plant growthpromoting
rhizobacteria (PGPR) strains provided a significant increase in shoot and root
length, and shoot and root biomass over the uninoculated control.
These results also indicate that the tested PGPR improved growth parameters in
tomato plants and contribute towards biocontrol of the tomato wilt pathogen.
