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Abstrak :
The plant growth promoting rhizobacteria (PGPR) is a group of bacteria capable of colonizing plants roots, thereby developing a system and improving plants growth and yield. The objectives of the study is to characterize the PGPR activities of several bacterial isolates {in-vitro screening), to examine their activities in stimulating soybean growth (in-vivo screening), and to identify the bacterial species. These were isolated from nodules and soil samples 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 includes the 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.). All bacterial isolates were identified using molecular methods based on nucleotide sequence generated from 16S rRNA gene. Three isolates 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. These isolates were B045 {Klebsiella variicola InaCC B827), B116 (Klebsiella sp. InaCC B833), and B210 {Mangrovibacterplantisponsorlaa.CC B841). The greenhouse assay showed that the plant height, plant dry weight and number of flowers in soybean seedlings significantly increased with Bradyrhispbium sp. strain 4167, then with Klebsiella sp. InaCC B833 and Mangrovibacterplantisponsor InaCC B841. These bacterial isolates which were characterized and screened in-vitro for PGPR potentials and their representative isolates which were identified by 16S rRNA sequence analysis are key factors for selecting PGPR isolates to be commercialized later as bio-stimulant.

Abstrak :
Saline soil is a common problem in coastal paddy field, especially in Indonesia. Salinity affects rice growth and the activities of soil functional microbes, including functional bacteria, which play roles in plant growth. Some of these microbes are associated with rice plants and are able to survive under saline condition. The presence of functional microbes is also important to improve soil quality. Nitrogen and phosphate are essential soil nutrients and is available in soil due to the activities of nitrogen-fixing bacteria and free-living plant-associated bacteria. The objective of the present study was to obtain nitrogen-fixing, phosphate solubilizing and Indole Acetic Acid  (IAA)-producing bacteria that are able to survive and promote the growth of rice under saline conditions. From rice and peanut rhizosphere, Ca-phosphate (Ca-P) solubilizing and nitrogen-fixing bacteria were isolated separately using specific media. Then, the Ca-P solubilizing ability, phosphomonoesterase activity and IAA-producing ability were quantitatively examined. Based on the abilities, 20 strains were selected and identified as Burkholderia cepacia-complex, Burkholderia anthina, Burkholderia cenocepacia, Bacillus cereus-complex (three strains), Achromobacter spanius, Azospirillum sp. (four strains), Azotobacter sp. (three strains), Rhizobium leguminosarum, Rhizobium sp. (two strains), and Pseudomonas sp. (three strains). The inoculation of several single strains or the mixture of the selected strains promoted the growth of rice under saline conditions. These inoculants could be potential as biofertilizer in saline paddy fields.