CHARACTERIZATION AND IDENTIFICATION OF PLANT GROWTH PROMOTING RHIZOBACTERIA ISOLATED FROM SOIL AND NODULE
The plant growth promoting rhizobacteria (PGPR) is a group of bacteria capable of colonizing plants roots thereby developing the system and improving plants growth and yield. The objectives of the study is to characterize PGPR activity of several bacterial isolates (in-vitro screening), examine their activities in stimulating soybean growth (in-vivo screening), and identify the potential of the bacteria. They were isolated from nodules and soil collected from Mount Pancar in Bogor, West Java Province as well as from Bangkirai Hill and Wain River in East Kalimantan, Indonesia. The in-vitro PGPR activity characterization include N-fixing ability, ACC-deaminase, indole acetic acid (IAA) production, cellulolytic activity, P-solubilization, Phosphomonoesterase (PME-ase), and nifH-gene detection. The in-vivo PGPR activity with the greenhouse assay was conducted on soybean plant (Glycine max L.) with a completely randomized design. All bacterial isolates were identified using molecular methods based on nucleotide sequence generated from 16S rRNA gene. Three isolate of soil and nodule bacteria with 7 characteristics of PGPR (N2 fixation, ACC-deaminase, cellulolytic activity, IAA production, solubilization index, P available, and PMEase activity) were successfully identified. The isolates were B045 (Klebsiella variicola InaCC B827), B116 (Klebsiella sp. InaCC B833), and B210 (Mangrovibacter plantisponsor InaCC B841). The results in greenhouse assay showed that the plant height, plant dry weight and number of flowers in soybean seedlings significantly increased with Bradyrhizobium sp. strain 4167, followed by Klebsiella sp. InaCC B833 and Mangrovibacter plantisponsor InaCC B841.The bacterial isolates which were characterized and screened in-vitro for PGPR potentials and representative isolates which were identified by 16S rRNA sequence analysis is a key factor for selection of PGPR isolates to be used in the future commercialization as bio-stimulant.
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