The investigation was conducted to search for novice strains of plant growth promoting rhizobacteria (PGPR) and apply them to apple trees with organic fertilizer to reduce the amount of chemical fertilizers. Twelve different bacterial isolates were isolated on Ashby’s medium from rhizosphere of healthy fruit trees. Screening process was achieved based on in vitro plant-growth-promoting features. The more potent bacterial isolate (B3) was selected for the subsequent experiments. Morphological and cultural characteristics and 16S rRNA gene partial sequence were used for identification obtained isolate. The 16S rRNA gene sequencing results revealed that the nearest bacterial species to our isolate was Enterobacter ludwigii, KJ638989.1, with about 98% matching. During 2019 and 2020 field traits were carried out to evaluate the effective role of E. ludwigii strain combined with doses of inorganic and organic fertilizers on “Anna” apple trees growth, yield and fruit quality. Data revealed that inoculation by E. ludwigii combined with compost could compensate 50% of chemical fertilizer with significant increment in growth, yield and fruit quality. Since, data showed high yield and fruits quality by using 50% mineral-NPK, compost (14 kg/tree) and E. ludwigii inoculant followed by treatment of 75% NPK, compost (7 kg/tree) and E. ludwigii inoculant. Finally, the obtained strain, E. ludwigii could be capitalized on promoting plant growth for various fruit crops since it exhibits reasonable potential characteristics.
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