Symbiotic Properties Of Rhizobium From Crotalaria Ocroleuca Used For Intercropping In Coffee Plantations In South-west Ethiopia

It has been established that the symbiosis between Rhizobium and legumes are a cheaper andrnusually more effective agronomic practice for ensuring an adequate supply of nitrogen forrnlegume based crop and pasture production than the application of nitrogen fertilizer.rnCrolotalaria ocroleuca is one of the members of crotalaria grown as cover crop or inter croprnin southern and south western parts of Ethiopia. Nineteen isolates were isolated from thernroot nodules of Crolotalaria ocroleuca from coffee growing area in Godere Wereda,rnGambella region under Teppi Coffee plantation Enterprise. Presumptive tests andrnmicroscopic features confirmed that the isolates were rod shaped and gram-negativernrhizobia. Based on colony and growth characters the isolates were grouped into two groups.rnAccordingly, 15 isolates were fast growing and acid producing Rhizobium spp; whereas fourrnisolates (AAUCR4.AAUCR9, AAUCR14 and AAUCR18) were slow growing and alkalirnproducing Brady rhizobium spp. Most of the isolates utilized the carbohydrates; sorbitol,rnxylose, and lactose, whereas only 26% and 15% were able to utilize starch and Na-citrate,rnrespectively. All isolates were resistant to kanamycin and erythromycin at lowerrnconcentration of 2.5 and 5 μm/ml. Only 68% and 79% were résistance at (2.5 μm/ml) andrn63% and 16% of the isolates were resistant at (5 μm/ml) to neomycin and gentamycin,rnrespectively whereas isolates (AAUCR9 and AAUCR18) were resistant to all the testedrnantibiotics. The isolates also showed variability in their physiological characteristics. Allrnisolates grew at 300C .while, 63% and 53% of the isolates were able to tolerate 150C andrn400C respectively. All isolates were able to grow at lower salt concentration (1-2%), and fivernisolates (26%) showed tolerance up to 4%. Only isolate (AAUCR9) was considered highlyrnosmo-tolerant since it grew at 5% of salt concentration. Amongst the isolates, 21% were ablernto form clear zones around their colonies on Pikovaskaya’s medium and hence, they werernconsidered as phosphate solubilisers with solubilisation index ranging from (2.2 -3). Relativerneffectiveness of the isolates was calculated by dry mass of the inoculated plant over the dryrnmass of positive control has significant difference within and among the treatment andrnpositive and negative control at (p

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