Effet de la salinité et des pesticides sur l’interaction plante-Pseudomonas spp : Cas de la fève (Vicia faba L.)

Abstract

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.