Isolation and Characterization of Sorghum Rhizosphere Bacteria Capable of Inhibiting Germination of Striga hermonthica (Del.) Benth Seed
Isolation and Characterization of Sorghum Rhizosphere Bacteria Capable of Inhibiting Germination of Striga hermonthica (Del.) Benth Seed
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Date
2015-06-15
Authors
Ibrahim Osman Basher, Noha
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Abstract
A study was carried out with the following objectives:
1- Isolation of sorghum rhizosphere bacteria that could be used as
bio-control agents for Striga hermonthica.
2- Development of application methods to test the efficiency of the
bacterial isolates as inhibitors of Striga hermonthica seed
germination and suppressers of seedling emergence.
3- Identification and general characterization of the efficient
isolates that inhibit striga seed germination.
Fifteen soil samples were collected from the rhizosphere of 10
sorghum cultivars grown in two locations: eleven samples from
Shambat (Fac. of Agric., University of Khartoum: Botanical garden
and glass house) and four samples from Elgadaref region in Eastern
Sudan to isolate bacteria capable of inhibiting Striga hermonthica
seed germination.
Fifty-four bacterial isolates were obtained using routine methods of
isolation. The efficacy of the isolates was tested for inhibiting Striga
hermonthica seed germination in preliminary in vitro experiments.
Out of the 54 isolates, 20 (13 from Shambat and 7 from Elgadaref)
showed good inhibitory effect to striga seed germination compared to
the control when applied at a dose of 5 μl of bacterial suspension.
Four isolates that showed very good inhibitory effect to striga seed
germination beside their promotion of sorghum growth were tested in
plastic bags experiments to evaluate the efficacy of these isolates in
inhibiting striga seed germination and seedlings emergence.
Three application methods were used; namely, coating sorghum seeds
with bacterial suspension, direct application of bacterial suspension on
sorghum seeds and shaking sorghum seeds with bacterial suspension.
Number of striga / sorghum plant, shoot and root fresh weight, shoot
and root dry weight and root: shoot ratio were used to evaluate the
efficacy of isolates in promotion of sorghum growth. There were
significant differences between the isolates efficiency. Coating
sorghum seeds with the bacterial suspension, using gum arabic as
carrier, were the best application method. This method was used to
evaluate the efficiency of 20 isolates in another plastic bags
experiment. The 20 isolates gave good inhibitory effect to striga seed
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germination. On the basis of microbiological and biochemical tests,
which are commonly used for identification of bacteria, the 20 isolates
were found to belong to the genus Bacillus and within the genus to the
species Bacillus coagulans, B. cereus, B. subtilis, B. licheniformis, B.
stearothermophilus, B. amyloliquefaciens, B. circulans and B.
thuringiensis
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