Evaluation of endophytic bacteria from some rice varieties for plant growth promoting activities

Abstract

Eighteen endophytic bacteria were isolated from different rice varieties by using Jensen’s nitrogen free medium. According to morphological and biochemical tests, isolates S1, R1, R2, R5 and R6 may be Rhizobium spp. and the remaining isolates may be Azospirillum spp. Fourteen out of isolates had plant growth hormone (Indole Acetic Acid) producing activity. R7 was the best Indole Acetic Acid producer among the isolated strains at two days incubation period in Jensen’s nitrogen free medium with L-tryptophan 0.5mg /ml at 37˚C and the concentration produced was 120.55 ppm. In nitrogen free semi-solid agar medium containing trace amount of bromothymol blue as indicator, all isolates showed nitrogen fixing activity during seven days incubation period. All isolates except S6 could solubilize phosphate on Pikovskaia’s medium supplemented with (0.5% Ca3(PO4)2). S5 was the best P- solubilizer at 5 days incubation period both in plate screening showing zone diameter 45mm and 539.78 ppm quantitatively. Fourteen isolates except (LS, R2, S4, S8) could also decompose potassium (ranging from 2-30mm in diameter) on K- decomposing medium with 0.12% Kmica. R3 was the best K-decomposer by plate screening (30mm in diameter) and 19.84 ppm quantitatively. S3 and R3 had good antagonistic activities against Rhizotonia solani and LS and R5 to Phythium spp. and S7 to Fusarium oxysporum respectively.