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

FAUZIA Y. HAFEEZ, M. AURANGZAIB KHAN*, SOHAIL HAMEED, EJAZ RASUL* AND KAUSER A. MALIK

Abstract: Effect of diurnally administered temperature regimes on the infection process of 3 Vigna spp., and 1Medicago sp., inoculated with GUS-marked (brady) rhizobial strains was examined. Conditions optimized for blue color development to indicate the presence of GUS-marked Rhizobium and Bradyrhizobium strains in the roots and nodules of inoculated plant showed significant results with 50 µg ml^-1 X-gluc buffer and 3 and 5 minutes of vacuum infiltration for young and mature nodules, respectively. Root hair colonization, curling, infection thread and nodule formation were observed in all the legumes at 30°C without any temperature shock. In V. radiata, no infection thread was found even at optimum temperature of 30°C. Root hair curling and infection thread formation were not observed in the genotypes exposed to temperature stresses, except in V. unguiculata, where the infection thread aborted in the root hair. Root hair colonization was observed a day after inoculation in plants subjected to both high or low temperature stresses, indicating the survival of (Brady)rhizobium strains under temperature stress conditions. The strains were unable to nodulate the host plants due to poor root hair development.

Institute for Biotechnology and Genetic Engineering, P. O. Box 577, Faisalabad, Pakistan.

Department of Botany, University of Agriculture, Faisalabad, Pakistan.