Phenotypic and plant growth promoting characteristics of Rhizobium leguminosarum bv. viciae from lentil growing areas of Ethiopia

Lentil (Lens culnaris Medik.) is an invaluable source of protein for the vast majority of Ethiopian people. It also maintains soil fertility through symbiotic nitrogen-fixation in association with Rhizobium leguminosarum bv. viciae. The aim of this study was selecting symbiotically efficient native lentil nodulating rhizobia endowed with different plant growth-promoting (PGP) characteristics. Hence, 30 lentil nodulating rhizobial isolates were isolated from soils collected from different farmer fields found in Central and Northern parts of the country. All isolates were characterized based on morphological, physiological, symbiotic and PGP characteristics. The result of this study showed that these isolates have exhibited interesting features such as wide range of carbon-sources and nitrogen sources utilization, tolerance to acidic and alkaline pH, metal toxicity and antibiotics.  Symbiotic characterization indicated that all tested isolates have showed great diversity in their capacity to nodulate their host plant and produce shoot dry matter yield under glasshouse conditions. In addition, they showed PGP characteristics such as IAA production and inorganic phosphate solubilization. Out of all tested isolates 36.7% of them were IAA producer while only 16.7% were insoluble inorganic phosphate solubilizer. In general, from the present study, it can be concluded that Ethiopian soils harbor highly efficient nitrogen-fixing lentil nodulating rhizobia which are diverse in their morphological, physiological and symbiotic characteristics.   Key words: Lentil, Rhizobium, Ethiopia, IAA production, phosphate solubilization.