Isolation and Characterization of Some Plant Growth Promoting Rhizobacteria (Pgpr) and Evaluation of Their Effects on Growth and Yield Performance of Tef [Eragrostis Tef (Zucc.) Trotter

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Date

2007-07-05

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Addis Ababa University

Abstract

A total of 162 bacteria were isolated from rhizosphere of tef [Eragrostis tef (Zucc.) Trotter] and characterized. Sixty six isolates were considered as plant growth-promoting rhizobacteria (PGPR) as determined by their plant growth promoting characteristics (Phosphate solubilization, antibiotic and HCN production) and further characterized by several morphological, physiological and biochemical tests and identified to species level using API kit method. Numerical analysis of phenotypic data by a computer cluster analysis using UPGMA (NTSYSpc software version 2.1) was done based on carbohydrate fermentation profile. Four isolates (AURB15, AURB34, AURB56 and AURB65) were also selected and inoculated on to two tef varieties (DZ-Cr-37 and DZ-01-974) at greenhouse condition to evaluate their effect on growth performance and yield of the tef varieties. The isolates displayed diverse morphological, physiological, biochemical and PGPR characteristics. Most of them were tolerant to wide range of temperature, pH and NaCl. The 66 isolates were found to belong to 7 genera and 15 species. Analysis of phenotypic data revealed that at boundary levels of 50% average similarity, two major clusters were formed by both Gram-negative and positive isolates while the respective groups form six and seven clusters at about 75% and 78.4% average similarity. Isolate AURB15 (Pseudomonas fluorscens) was observed to significantly increase mean root dry weight (39%), root shoot ratio (42%) and yield (45%) of the tef variety DZ-Cr-37; like wise isolate AURB65 (Bacillus subtilis) better increased mean root dry weight (28%), root shoot ratio (19%) and yield (44%) of tef variety DZ-01-974 compared to the control groups. Inoculation of all the four isolates resulted in comparable mean shoot dry weight with the control groups (p > 0.05). Where as inoculation of two isolates, AURB34 (Burkholderia cepacia) and AURB56 (Bacillus coagulans) on DZ-01-974 failed to increase mean root dry weight, root shoot ratio and yield of DZ-01-974. No significant variation of percentage nitrogen and total protein was observed by inoculation (p > 0.05). The increase in mean root dry weight, root shoot ratio and yield of tef varieties DZ-Cr-37 and DZ-01-974 by AURB15 (Pseudomonas fluorscens) and AURB65 (Bacillus subtilis) suggests that the isolates have better potential for further field testing and application in improving yield of the tef varieties.

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Keywords

Isolation, Characterization, Growth Promoting, Rhizobacteria, Growth and Yield, Performance, Tef, Trotter

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