Survival of Pseudomonas extremorientalis TSAU20 and P. chlororaphis TSAU13 in the rhizosphere of common bean (Phaseolus vulgaris) under saline conditions

The abilities of Pseudomonas extremorientalis TSAU20 and P. chlororaphis TSAU13 to colonise and survive in the rhizosphere of common bean under saline conditions were studied. Four salinity levels (5.0, 7.5, 10.0, and 12.5 dS/m) were maintained in the gnotobiotic system using NaCl salt. Results showed that with increasing salt content root-tip colonization of both bacterial strains was reduced. Both bacterial treatments used in the study increased root and/or shoot length compared to non-treated plants at each NaCl concentration tested, whereas shoot growth was not stimulated at high saline condition (12.5 dS/m). In conclusion, the results of this study indicated that P. extremorientalis TSAU20 and P. chlororaphis TSAU 13 have the ability to survive in ecologically stressed conditions, such as saline and nitrogen deficient soils, and may positively effect on plant growth of bean. High salinity inhibited their colonisation in the rhizosphere of bean and thus their stimulatory effect on plants was also reduced.