USE OF GUS-MARKED RHIZOBIUM AND BRADYRHIZOBIUM STRAINS FOR STUDYING THE EFFECT OF TEMPERATURE ON THE INFECTION PROCESS

Effect of diurnally administered temperature regimes on the infection process of 3 Vigna spy., and 1 Medicago sp., inoculated with GUS-marke d (brady) rhizobial strains was examined. Conditions optimized for blu e color development to indicate the presence of GUS-marked Rhizobium a nd Bradyrhizobium strains in the roots and nodules of inoculated plant s showed significant results with 50 mu g ml(-1) X-gluc buffer and 3 a nd 5 minutes of vacuum infiltration for young and mature nodules, resp ectively. Root hair colonization, curling, infection thread and nodule formation were observed in all the legumes at 30 degrees C without an y temperature shock. In V. radiata, no infection thread was found even at optimum temperature of 30 degrees C. Root hair curling and infecti on thread formation were not observed in the genotypes exposed to temp erature stresses, except in V. unguiculata, where the infection thread aborted in the root hair. Root hair colonization wa's observed a day after inoculation in plants subjected to both high or low temperature stresses, indicating the survival of (Brady)rhizobium strains under te mperature stress conditions. The strains were unable to nodulate the h ost plants due to poor root hair development.