Symbiotic effectiveness of indigenous rhizobia nodulating field pea (Pisum sativum L.) on soils of Horro Guduru and East Wollega highlands in western Ethiopia

Abstract

Field pea (Pisum sativum) production in Ethiopia is low due to low soil fertility, particularly Nitrogen (N) deficiency Screening and selecting the most effective strain is important for effective biological nitrogen fixation. This study was initiated to characterize and evaluate symbiotic effectiveness of field pea rhizobia collected from East Wollega and Horro Guduru Wollega zones, Ethiopia. Thirty two rhizobial isolates from field pea collected from the zones were isolated and phenotypically characterized under laboratory conditions. The results showed that all 32 isolates exhibited typical colony characteristics of fast growing rhizobia. The majority of isolates displayed large mucoid (50.4%) and watery colony texture (40.6%) and attained colony sizes ranging from 2.8–6.0 mm with generation time between 1.8 and 4.5 h. A number of isolates (41%) displayed phosphorus solubilization ability with phosphate solubilization indices (SI) ranging from 1.1 to 2%. Most of the isolates grew at pH values ranging from 4.5–9.0, concentrations of NaCl (1–4%), and displayed tolerance to 10 to 45°C incubation temperatures. Twenty nine isolates were evaluated for their symbiotic effectiveness on sand pot experiment in green house in Holeta Research Centre in 2015. The data showed that 94.4% of the isolates performed best in symbiotic nitrogen fixation from which 36.4% were highly effective and 62% were effective. The inoculated plants also showed differences in plant tissue nitrogen content which ranged from 1.72 to 2.93%. The highly effective isolates were nutritionally versatile and ecologically competitive and hence deserve recommendation for further tests under field conditions to enhance field pea production.

Keywords/phrases: Burkitu, Competence, Heterotrophic, Rhizobia