INVESTIGATING RHIZOBIUM BACTERIA AND OBTAINING SALINITY TOLRANCE ISOLATES USING GENETIC TRANSFORMATION METHOD
AbstractThis study was conducted to isolate Rhizobium from the roots of wild and field cereal plants (Trifollium spp. , Medicago sativa , Ficia vaba , Pisum sativum , Medicago polymorpha L. , Melilotus indica (L.) ALL , Sesbania spp. , (Trigonella coerulescens M.Bieb ) ,30 isolates strains from plants roots were obtained , 15 from wild cereal and 15 from field cereal, The most efficient nitrogen fixing 8 isolates have been selected on the basis of the diameter of the colony and that of the change of the blue color of the medium of the promothymol blue indicator YEMA-BTB .The optimal conditions for the development of the selected isolates have been studied in terms of temperature, pH and their endurance of the salinity of the medium. Consequently, the best wild isolate,PW7 is taken from wild Sesbania the best field isolate designated PF12 isolated from Medicago sativa , the genetic content of these selected strains were studied, the results showed that the two strains contain small plasmide bands, PF12 strains contains an additional large plasmide band, in order to study the role of these plasmids in the genetic experiment was conducted to neutralize these plasmids by using salsalic acid, results showed that the neutralize cells lost their salinity resistance when tested on a YEMA medium with varying concentrations , genetic transformation was conducted by carrying the DNA extracted from strain PW7 into strain PF12.results showed the transference of the plasmids from PW7 to PF12 which transferred the salinity resistance trait . This has been confirmed by re-culturing the transformed isolate onto the YEMA medium with different salinity concentrations. The modified isolate could grow in a salinity concentration of 8% NaCL.
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