Hup phenotype and serogroup identity of soybean-nodulating bacteria isolated from Japanese Soil

Eighty-five isolates of Bradyrhizobium japonicum obtained from 46 soils in various areas of Japan were examined for the uptake hydrogenase (Hup) trait and somatic serogroup identity. Uptake hydrogenase positive (Hup+) phenotype occurred in 34% of the total isolates, and in half of the soils examined. Relative frequency of serogroup was different from that reported in the U.s.a. The most predominant serogroup was 110 to which 27% of the isolates belonged. High frequencies of Hup+ isolates were found in the serogroups 122 and 110, accounting for 100 and 74% of the total, respectively. It was suggested that there was a relationship between the Hup phenotype and serogroup.