| Summary: | Rhizobia are bacteria that able to associate with legumes commonly called Legume Nodulating Bacteria (LNB). The bacteria are able to form nodules by infecting plant roots. The existence of this association is called cross inoculation group. Cross inoculation group is group of rhizobia that able to form nodules on the roots of specific legumes. The association is due to the different characteristics of each root nodulating bacteria. These characteristics can be used as the basic of biofertilizers manufacturing. The objective of this research was to investigate the characteristics of 10 bacterial isolates based on phenotypic traits and the ability of forming nodules and fixing nitrogen of some legumes. Characteristics of soil rhizobia can be analyzed based on phenotypic properties. Ten bacteria isolates used in this research were obtained from several agroecosystems in Sumberjaya, Lampung. Analysis was performed based on phenotypic traits such as cell and colony morphology, biochemical properties, nodule formation test in some legumes, such as: Siratro (Macroptillium atropurpureum), Soybean (Glycine max), red beans (Vigna angularis), Lamtoro (Leucaena leucochephala), Sengon Laut (Albizia falcataria), Kembang Telang (Clitoria ternatea), and Lima bean (Phaseolus lunatus), and nitrogen fixing test by using Acethylene Reduction Assay (ARA) method. The result showed that 10 isolates of bacteria were Gram negatif as well as
Bradyrhizobium japonicum USDA122 and THA7. When grown on medium Congo
Red Yeast Mannitol Agar (CRYMA) showed 7 isolates were pink colour the same as
Bradyrhizobium japonicum USDA122, and 3 isolates were white as well as
Bradyrhizobium japonicum THA7. Based on biochemical testing, 7 isolates had
similarity with Bradyrhizobium japonicum THA7 and 3 isolates had similarity with
Bradyrhizobium japonicum USDA122. The results of root nodules formation test,
there were 3 isolates, Rhizobium sp. TANU 14/ Agrobacterium veiscosum,
Pseudomonas stutzeri, and Azospira could form nodules on 6 legumes as well as
Bradyrhizobium japonicum USDA122 and THA7. Based on the ability of forming
nodules, 10 isolates formed nodules on Siratro, Soybean, Red bean, Sengon Laut, and
Kembang Telang. Kembang Telang had wide spectrum and could be potentially used
as a trapping crop. The highest nitrogenase activity obtained on Bacillus cereus
(12.2) in siratro (13,545 mmol N2.g nodules-1.h-1), althought the nitrogenase activity in soybean was low (0,038 mmol N2.g nodules-1.h-1).
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