Phenotypic Characteristics and Symbiotic Effectiveness of Field Pea (Pisum Sativum L.) Rhizobia From Some Central Part of Ethiopia Under Greenhouse Condition
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Date
2018-06-05
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Addis Ababa University
Abstract
Nitrogen is one of the most abundant elements, and biological nitrogen fixation (BNF) is the main source of nitrogen for legume plants. Field pea is one of the most important legume plants which is grown in Central Showa High Lands. This study was initiated with the objectives of isolating and characterizing root nodule bacteria from three routes of Central Showa, and evaluating their symbiotic effectiveness on field pea under green house conditions in order to boost crop productivity. Root nodules were collected from young and healthy seedlings of Pisum sativum L. from farmer’s fields at different locations (Debre birhan, Fitche and Ambo) of Central Showa. Twenty seven Rhizobial isolates were retrieved from the root nodules of Pisum sativum and characterized by standard biochemical tests. Average generation time was between 2.0 to 4hrs. All the isolates were gram-negative and did not absorb red color when cultured on Yeast Extract Manitol Agar containing Congo red. All the strains utilized glucose, D-mannitol, and sucrose. Only 17% Rhizobium isolates tolerated 6% NaCl. The isolates were tentatively identified as Rhizobium leguminosarum. All the isolates formed watery and mucoid colonies on YEMA medium, and failed to grow on peptone glucose agar medium and to solubilize inorganic phosphate. Almost all the isolates were tolerant to pH 5 to 9, salt concentration (1-2%), and temperature of 250C to 350C. The isolates were also tolerant to ampicillin, penicillin, erythromycin and chloramphenicol, but sensitive to gentamycin and tetracycline. The isolates were diverse in amino acid utilization in which about 22% of the isolates were utilized all the amino acids used and also they showed variation in heavy metal resistance in which most of the isolates resisted Al and Mn. About 34% of the isolates were highly effective and 48% effective whereas 7% were lowly effective and 11% ineffective. AAURFP35, AAURFP36, AAURFP37, AAURFP38 and AAURFP39 were the isolates that showed good physiological, eco-physiological and symbiotic characteristics and need further testing under different environmental conditions in the field to be used as effective bio inoculant in field pea cultivation.
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Keywords
Field Pea, Growth Factors, Inoculant, Nitrogen Fixation, Rhizobium