Detection and Identification of Plant Growth Promoting Bacteria from Sorghum (Sorghum bicolor L. Moench) Rhizosphere Soil in Northern Ethiopia

Birhanu Babiye,Taye Tessema,Beira H Meressa

doi:10.13005/bbra/2935

Abstract

Plant growth promoting rhizobacteria are the bacteria which subsist inside and outside of the plant tissue and promote plant growth through direct or indirect mechanisms. To increase sorghum production and productivity we utilize herbicides and chemical fertilizers to overcome sorghum production constraints, but those chemicals have negative side effects. The current study was conducted with the objective of isolation of PGPR from sorghum rhizosphere and screening for primary growth related trait, evaluation of potential PGPR at greenhouse for sorghum growth performance and identify through biochemical characterization. So that, in this study a total of 117 plant growth promoting rhizobacteria were isolated from the rhizosphere of 12 sorghum (Sorghum bicolor L. Moench) genotype by cultivating using 3 collected soil samples from the northern part of Ethiopia (Amhara and Tigray regional states) in greenhouse. Isolated bacteria were screened for primary growth promoting traits such as phosphate solubilization test, IAA production test at different concentration of L-tryptophan and ammonia production test. From the isolated bacteria 28% solubilized Phosphorous, 78% produced IAA at different concentration of tryptophan. The greatest IAA production was scored at 100 mg/L of tryptophan and the lowest production of IAA was scored at 150 mg/L of tryptophan, 69% of isolated bacteria produced ammonia. Hence, 15% of isolated bacteria fulfilled the above primary screening test and used for further greenhouse evaluation. Accordingly, eighteen bacteria were tested for greenhouse experiment using completely randomized design and all 18 isolates were significantly increased all the agronomic parameter as compared to the control such as plant shoot height, plant shoot fresh and dry weight, root length, root fresh and dry weight at p < 0.01 and P ≤ 0.001. Two isolates G6E29 and G4E19 had significantly increased all the parameter but two isolates (G12E19 and G3E40) were statistically non-significant for root fresh weight compared to the control. These 18 potential isolates were characterized morphologically and biochemically. Eight isolates were grouped at Pseudomonas genera. Six isolates were grouped at Azotobacter and the rest four isolates were grouped at Bacillus genera. Thus, the use of plant growth promoting rhizosphere bacteria could be useful to improve sorghum production and productivity. However, further molecular identification and evaluation of the isolates exhibiting multiple plant growths promoting traits on plant-microbe interaction for economic crop of Ethiopia is needed to uncover their efficacy as effective plant growth promoting rhizosphere bacteria.

Highlights

Plant growth promoting rhizobacteria are the bacteria which subsist inside and outside of the plant tissue and promote plant growth through direct or indirect mechanisms
The current study reports that all the isolates significantly increased the root fresh weight with different amount, these might be due to the tested sorghum genotype genetic makeup and environmental condition is comfortable for PGPR, as well as each isolate might have different potential based on their genome and colonize the root to increase the root fresh weight or the sorghum genotype that more carbon root exudates which is used for PGPR to colonize the root 40
The result of the current study revealed that the objective such as to isolate and screen isolated PGPR for growth promoting trait and evaluate their growth promoting potential in the greenhouse and identify potential growth promoting PGPR using biochemical and morphological characterization which are isolated from 12 sorghum genotype by cultivating on 3 collected soil samples from Northern part of Ethiopia

Summary

Introduction

Plant growth promoting rhizobacteria are the bacteria which subsist inside and outside of the plant tissue and promote plant growth through direct or indirect mechanisms. Isolated bacteria were screened for primary growth promoting traits such as phosphate solubilization test, IAA production test at different concentration of L-tryptophan and ammonia production test. Further molecular identification and evaluation of the isolates exhibiting multiple plant growths promoting traits on plant-microbe interaction for economic crop of Ethiopia is needed to uncover their efficacy as effective plant growth promoting rhizosphere bacteria. Compared to other African countries, Ethiopian sorghum productivity is very low with an average productivity of 2.7 tons per ha This low productivity needs sorghum improvement to increase productivity to achieve food security.[11,17, 20] Both abiotic and biotic factors; such as drought, low soil fertility, insects, quelea bird and Striga weed are the major production constraints affecting sorghum productivity.[16, 24]

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Results

Conclusion