Tolerance of Bradyrhizobium sp (Lupini) strains to salinity, pH, CaCO3 andantibiotics

Aims: Ten rhizobial isolates obtained from different locations in Egypt wer e examined for their ability to survive under stress conditions and their g rowth 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 concentrat ion up to 5% and were divided into two groups with respect to NaCl toleranc e. The rhizobial isolates from group two showed significantly (P < 0.05) be tter survival under high NaCl concentration. All the tested isolates surviv ed acidic (pH 4-5) and alkaline conditions (pH 9-10) and CaCO3 (up to 10% w /v) in liqued YEM medium. Conclusions: Antibiotic resistance patterns did not correlate to NaCl, pH o r 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 ino culants for successful lupin growth.