Simple method of genomic DNA extraction from Rhizobia in dried nodules of Phaseolus vulgaris for strain differentiation by PCR-based DNA fingerprinting

Repetitive DNA peR fingerprinting of bacterial genomic DNA is a useful tool for typing and differentiation of rhizobial strains. The method was reported to be suitable for strain differentiation of Rhizobia present in individual root nodules of some leguminous plants without the need for isolation and cultivation of the strains, in which rhizobial genomic DNA was extracted directly from each fresh or frozen nodule. We developed a new protocol of rhizobial genomic DNA extraction/purification from dried nodules of Phaseolus vulgaris for generating repetitive DNA peR fingerprints of Rhizobia present in the nodules. The simplified protocol consists of only three major steps, heat extraction of genomic DNA from rhizobial cells prepared from dried nodules, ethanol precipitation of the DNA and Sephadex G-50 column purification of the DNA, and generated fingerprints with good quality for differentiation of Rhizobia strains. The protocol will be useful to examine the nodule occupancy of inoculated rhizobial strains in field experiments.