Spatial distribution pattern of Rhizobium leguminosarum bv. vicieae across legume growing areas of Tigray region

Abstract

Introduction: Several research findings stated that, faba bean had phenotypically diverse and symbiotically effective in Tigray, Ethiopia. However, limited researches were conducted in the region regarding biological nitrogen fixation with local varieties and races. Objective: To address the limitations Spatial Distribution Pattern of Rhizobium leguminosarum bv. Vicieae across legume growing areas of Tigray region was investigated. Methodology: A total of 112 root nodules with (107.9 average) nodules plant-1 were collected from 15 major faba bean growing districts of the region for isolation and characterization of indigenous root nodulating bacteria of the host plant. A serious of methods and procedures were undertaken to confirm the presumptive, eco-physiological and morphological characteristics of the isolated Rhizobium bacteria in triplicates. Results: All the tested isolates were presumptively gram -ve, raised, translucent and white in color, failed to grow on peptone glucose agar, keto lactose test and Hofer’s alkaline test. Phenotypically, 75% of the isolated candidates were appearing large mucoid and morphologically >80% of them were recorded more than 2mm colony diameter. Physiologically, 100 % of the isolates were grown well at a temperature range between 20℃ and 30℃, pH values between 6 and 8, and in the range of 0.1 and 2.5% (w/v) NaCl concentrations. In addition to this, a faba bean nodulating bacterium uses a broad range (90-100%) of carbohydrate utilization. The effectiveness of the candidates confirms 65%, 18.33%, 15% and 1.6% were recorded as highly effective, effective, less effective and ineffective. Moreover, the highest and lowest symbiotic effectiveness was scored 457% and 21% respectively.