Phosphate-Solubilizing and Auxin-Producing Rhizobacteria Promote Plant Growth Under Saline Conditions
Meftah Kadmiri, Issam
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The world loses 3 ha of arable lands every minute due to salinization. To counteract adverse effects of salinity on plants, the use of PGPR is an efﬁcient/cheaper method that induces salt stress tolerance in plants. The aim of the present work was to study auxin production and inorganic phosphate solubilization capacities of Pseudomonas ﬂuorescens Ms-01 (A newly isolated strain from grapevine rhizosphere) and Azosprillum brasilense DSM1690 (DSMZ strain isolated from Digitaria decumbens roots) under hypersaline conditions. The objective was to assess their synergetic action in the promotion of wheat plant growth in saline conditions. The results showed a prominent ability of the studied strains to grow in high NaCl concentrations of about 600mM. In addition, both auxin production and phosphate solubilization activities were maintained in hypersaline conditions. In fact, with an initial IAA production of 32µgml−1, A. brasilense DSM 1690 maintained a good production in hypersaline conditions (22.5±4.1µgml−1 in 400mM NaCl). Phosphate solubilization activity of P. ﬂuorescens Ms-01 was also signiﬁcantly improved with increase in salinity, reaching 22.6±1.7µgml−1 P2O5 in 600mM NaCl. The inoculation of wheat plants with the studied bacteria increased the plant height and weight under normal and saline conditions. Results showed signiﬁcant increase in proline accumulation and in the activity of POD and APX antioxidant enzymes in wheat plants inoculated with P. ﬂuorescens Ms-01 in saline soil conditions. The correlation between proline accumulation and antioxidant enzymes activities indicated that the inoculation improved the defense pathway of plants against salt stress.