Résumé:
Salinity and accumulation of pesticides residues in soils represent serious constraints for
plants. This can induce high levels of stress, reducing biomass and altering physiological and
biochemical processes in plants. For this purpose, researchers have often studied the effect of
plant growth promoting rhyzobacteria (PGPR) as promoter and enhancer the plant growth
under abiotic stress. In this study, tree Pseudomonas strains were isolated (P1 and P7
from a saline soil, and P15 from a vineyard soil treated with copper). The isolates were and
screened by salinity and copper tolerance. the role of this bacterial isolates in reducing the affect
of salt and cooper stress on germination, growth and physiology of bean Vicia faba (OTONO
variety) was examined in presence of 100 and 150 mM.l-1 of NaCl and 2,5 ; 10 and 20 mM.l-1
of CuSO4 respectively.
According to the results obtained, under salinity stress, the percentage of germination
of the inoculated and non-inoculated bean seeds with bacterian strains was decreased in
proportion to the concentrations of NaCl. Salinity has also decreased the production
of biomass, total chlorophyll content and the Na+/ K+ ratio. We also observed the the salinity
increased the proline accumulation in inoculated and uninoculated
plants. However, inoculation of the bean seeds with P1 and P15 strains showed no effect on the
rate and speed of germination, in both presence and absence of salt stress,
whereas P7 has significantly increased the rate of germination. We also found that inoculation of
the bean plants with the P1, P7 and P15 strains increased significantly the production
of fresh biomass, in presence and absence of salt stress, and affected positively the accumulation
of proline and the Na+/ K+ ratio. Only P1 strain increased total chlorophyll content in plants.
Under copper stress conditions with and without baccterial inoculation, no significant
effect of copper, has been recorded on the germination rate. Whereas, the production of biomass
and total chlorophyll content were significantly decreased by copper stress. Copper traitement
increased proline content in inoculated plants with P7 and P15 isolate and uninoculated, however
this content was decreased in inoculated plants whith P1. Only the inoculation with P1 strain
showed an increasing effect on the germination potential under 20 mM.l-1 copper traetment, while
inoculation with P1, P7 and P15 stimulated production of fresh biomass and accumulation of
proline, and otherwise decreased total chlorophyll content in plants.
