Salt and pH stress tolerating plant growth promoting rhizobacteria from multivarietal mango orchards

The adverse effects of biotic and abiotic stress on various horticultural crops can be overcome by inoculating the roots with stress tolerating plant growth promoting bacteria. In our study, 7 bacteria were isolated from multivarietal mango orchards of Chittoor district of Andhra Pradesh and characterized based on morphological and biochemical tests. Among all the isolates, K1 and K3 were able to tolerate up to 10% NaCl concentration at all the pH (7, 8 and 9). P solubilzation of the isolates ranged from 9.70 to 25.39 pg/ml; ZnCO3 from 0.61 to 2.64, ZnO from 1.76 to 2.55, Zn-3(PO4)(2) from 1.07 to 2.47 mg/L; IAA, GA(3) and ABA production ranged from 607 to 906 ng/ml, 308 to 1096 ng/ml and 189 to 762 ng/ml of broth respectively. Isolate K3 was found to be more effective against Fusarium oxysporum and Colletotrichum gloeosporioides with the maximum inhibition of 46.42% and 58.46% respectively. Molecular confirmation of strains K1 showed 99 % similarity with Providencia vermicola (Accession no: MK942853) and K3 with 98% similarity of Providencia rettgeri (Accession no: MH588071). The identified strain K1 and K3 from our study had a high potential for use particularly under stress conditions.