Charactaraization and Selection of Rhizobium Strains for stress condition under Semi-arid Environment in Sudan

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.