Isolation, Identification and Evaluation of the Plant Growth Promoting Activities of Endophytic Stenotrophomonas maltophilia to Stimulate Growth of Clover Plants under Salt Stress

Two endophytic bacterial isolates were obtained from root nodules of clover plants grown in salt affected clay soil of Egypt. The isolates were closely linked to Stenotrophomonas maltophilia strains IPR-Pv696 and 262XG2 based on the sequencing and phylogenetic analysis of 16S rRNA genes, and deposited in GenBank with accession numbers OM980221.1 (AM1) and OM980223.1 (AM2) respectively. The isolates were evaluated for their potential to promote plant growth. The results revealed that the two isolates of S. maltophilia strains (IPR-Pv696 and 262XG2) respectively exhibited production for indole-3- acetic acid (30.26 & 31.15 µg/ml), exopolysaccharides (13.57 & 13.68 g/l), nitrogen fixation activity and they solubilize the phosphate (278 & 208 mg/l) and potassium (33.5 & 32.9 µg/ml). In a field trial, these two isolates increased clover plant growth, chlorophyll, carbohydrates content and nutrients uptake while lowering proline levels. Hence this highlights its application to be exploited as biofertilizer by leading to sustainable agriculture. This could be a promising inoculant for many other crops.