Abstract:
The root environment of leguminous crops undergoes constant changes as a result of
chemical reactions taking place within the soil .Rhizobia produces root nodules is subject
to changes in the soil environmental conditions including salt concentrations, pH and
temperature.
In this study, four Rhizobium strains have been used for screening their stress tolerating
ability. The cultural ,microscopic and, biochemical characteristics were studied for all the
isolates.
Growth of pure Rhizobium strains on Yeast Extract Mannitol Agar (YEMA) medium
having variable range of pH (6.0, 8.0and 10), different concentrations of NaCl (0%,
0.1%, 0.5%, 1 % and 2% ) and different incubation temperatures (200C, 300C and 400C)
was studied .
The results revealed that the optimum growth for the tested strains was under the low
concentrations of NaCl (0% and 0.1% NaCl) .pH 8 was the best pH level for the tested
strains The highest population growth for the tested isolates was at 300C.
From the general results under the different stresses strain USDA 3386 was selected as
the superior strain as it had the best performance at the different stresses therefore, it can
be utilized in the stressed environments.
