Tolerance of Bradyrhizobium sp. (Lupini) strains to salinity, pH, CaCO3 and antibiotics

Abstract

AIMS: Ten rhizobial isolates obtained from different locations in Egypt were examined for their ability to survive under stress conditions and their growth response to increasing levels of NaCl (1-8% w/v), pH (4-10), CaCO3 (1-10% w/v) and 12 antibiotics. METHODS AND RESULTS: All the rhizobial isolates tolerated a NaCl concentration up to 5% and were divided into two groups with respect to NaCl tolerance. The rhizobial isolates from group two showed significantly (P < 0.05) better survival under high NaCl concentration. All the tested isolates survived acidic (pH 4-5) and alkaline conditions (pH 9-10) and CaCO3 (up to 10% w/v) in liqued YEM medium. CONCLUSION: Antibiotic resistance patterns did not correlate to NaCl, pH or CaCO3 tolerance. Variations among different strains showed that there is potential to improve strain performance under stress conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The results suggest that selection of adapted strains under stress conditions is possible and can be used as inoculants for successful lupin growth.