Isolation and Characterization of Salt Tolerant Strains of Sinorltizobium meliloti

Raad Sultan,Fawaz Al-Safar

doi:10.33899/edusj.2007.162948

Abstract

Twenty four strains of Sinorhizobium meliloti were isolated from root nodules of alfalfa plants. Host plants collected from different agroclimatic regions of Ninavah province-Iraq. Five strains, vis. FA7, FA8, FAlO, FAll and FA12 were found tolerant to 6% NaCI. All the five strains were able to grow on rhizobia! minimal medium. The five studied strains showed multiple antibiotic resistance. The more sufficient production in shoot group in alfalfa plants found when the plants inoculated with F A8 and FA 7 strains. pH changes in MSY solid medium study revealed that changes in pH towards acidity. Reduction in colony forming units (CFU) was observed under salt conditions in comparison with normal conditions. Production of cell surface molecules in these five strains , such as, P-(1 ----+ 3) glucans, cellulose fibrils and exopolysaccharides were also studied. Heat curing of Sym plasmids study revealed that at least one of the salt tolerant genes lays on Sym plasmids.

Highlights

Atmospheric N2 fixed symbiotically by the association between Rhizobium species and legumes represents a renewable source of N for agriculture [1]
The more sufficient production in shoot group in alfalfa plants found when the plants inoculated with FA8 and FA7 strains. pH changes in Mannitol Salt Yeast Extract (MSY) solid medium study revealed that changes in pH towards acidity
FA12 could grow on MSY medium supported with 6% NaCl, 8% K2S04 and pH 4.5 choosed for further studies

Summary

Introduction

Atmospheric N2 fixed symbiotically by the association between Rhizobium species and legumes represents a renewable source of N for agriculture [1]. 7. Screening for salt tolerance The growth of all isolated strains of S. meliloti was tested by streaking these strains on MSY medium containing (0, 2, 4, 6 and 8 %) of NaCl. Incubation was done at 28±2 oc for 4-6 days (21 ). To confirm symbiotic plasmids curing; plant nodulation test, antibiotic sensitivity and 6 % NaCl tolerance were done as reported by Vincent [15], Hussein [20] and Sadowsky eta/.

Results

Conclusion