Diversity of Rhizobacteria Associated with Sorghum Wild Relatives in Assosa Zone of Ethiopia and Their Ability to Solubilize Phosphate

Eleni Belay,Befekadu Teshome

doi:10.11648/j.fem.20210702.13

Abstract

Culture based diversity of Rhizobacteria associated with Sorghum wild relatives were identified by this study. Rhizobacteria, which include rhizosphere bacteria, rhizoplane bacteria and endophytic bacteria were isolated and identified. The isolates were also evaluated and screened for their ability to solubilize phosphates on Pikovskaya’s agar plates. One hundred twenty-six rhizobacteria were isolated on nutrient agar from the samples. Out of these Rhizobacterial isolates, 21 of them were endophyte bacteria, 40 of them were rhizosphere bacteria and 65 of them were rhizoplane bacteria. The 126 isolated rhizobacteria were clustered into 36 similar representative Morphotype groups. And, they were identified using GEN III Biolog microbial identification system. Gram negative rhizobacteria were more predominant than Gram positive rhizobacteria. Genus Pseudomonas was found as the most dominant Rhizobacterial taxa among the identified P-solubilizing Rhizobacteria and Non-P-solubilizing Rhizobacteria isolates. Forty seven percent (47.2%) of the clustered rhizobacterial isolates showed clearly visible haloes (>0.50 cm) around their colonies on Pikovskaya’s agar after seven days of incubation at 30 ± 2°C. They showed a significant difference of solubilization index (SI) [p<0.05] and ranged from 1.3 to 5.3 with a mean value of 2.4. Gram positive bacteria (Bacillus cibi) produced the largest solubilisation index when compared with the Gram-negative isolates. This study indicated that P-solubilizing rhizobacteria associated with Sorghum Wild Relative have very large phosphate solubilization index. Thus, it is recommended to include them in research programs that intend to screen P-solubilizing bacteria for microbial inoculant development.

Highlights

Diverse microorganisms which exist around the plant rhizosphere modulate the physiology and morphology of plants and by that they improve plant growth through hormone production, nutrient uptake and protecting plants from pathogens [3, 19]
Out of these Rhizobacterial isolates, 21 of them were endophyte bacteria which were isolated from root, 40 of them were rhizosphere bacteria which were isolated from rhizosphere soil and 65 of them were rhizoplane bacteria which were isolated from the root washing solutions
The result indicated that a greater number of rhizobacteria is isolated from the soil and root washing solutions than the rhizobacteria isolated from the root

Summary

Introduction

Diverse microorganisms which exist around the plant rhizosphere modulate the physiology and morphology of plants and by that they improve plant growth through hormone production, nutrient uptake and protecting plants from pathogens [3, 19]. The dominant bacteria which colonize this zone are known as rhizobacteria [8]. They are characterized by aggressive colonization and subsequent establishment on plant roots. Some of this diverse bacterial species are culturable and others are yet unculturable. Multiple interactions occur among the plant root, soil and bacteria in the dynamic environment of the rhizosphere. Rhizodeposits are suitable for binding bacteria and such environments are richer in microflora and available nutrients than the bulk soil [3]. The different forms of the rhizodeposits facilitate below-ground interactions between plants and microorganisms and affect the biodiversity of the rhizosphere. Root–microbial interactions involve myriads of microorganisms and are very

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Conclusion