Identification of strains of Mesorhizobium huakuii, root nodule bacteria of Astragalus sinicus, by the polymerase chain reaction

Abstract

Strains of Mesorhizobium huakuii, root nodule bacteria of Astragalus sinicus, were identified from DNA polymorphism amplified by the polymerase chain reaction (PCR) using some known or random primers. Five strains of M. huakuii isolated in Japan and China were examined using SPH (a random primer), nifHDK (a part of the sequence of nif gene) and ERIC (both ends of an repetitive intergenic consensus DNA sequence of enteric bacteria). DNA bands amplified with primers showed distinctly different band patterns between groups of strains isolated in Japan and those isolated in China. Although it was sometimes difficult to identify strains belonging to the same group with only one primer, strains of a group could be identified by comparison of the results obtained with different PCR primers. Strains of M. huakuii isolated randomly from a rice field soil were examined by PCR, and several types of strains were found to survive at the same site. This identification method using PCR was also useful to investigate the infection rate of inoculated strains in a pot cultivation experiment.