DIFFERENCES AMONG STRAINS OF BRADYRHIZOBIUM IN FATTY-ACID METHYL-ESTER ANALYSIS

Fatty acid-methyl ester (FAME) and two-dimensional principal component analysis of 89 strains of Bradyrhizobium, most of which were from soy bean, distinguished five groups of bradyrhizobia. These included one c luster containing several isolates previously designated as Bradyrhizo bium elkanii, and two related clusters containing strains previously i dentified as belonging to Bradyrhizobium japonicum groups IA and IB. N ot all of the organisms evaluated clustered with the B, japonicum and B. elkanii strains. A number of Bradyrhizobium strains isolated from s oybean in Korea and northern Thailand had FAME profiles so different f rom the B. japonicum and B. elkanii strains as to warrant separation a t the species level. A slow-growing isolate from Lupinus also had a FA ME profile very different from those of the other bradyrhizobia. Resul ts obtained in this study were generally in agreement with those obtai ned using other taxonomic approaches, suggesting that FAME analysis pr ovides a relatively simple and reliable procedure for the initial char acterization of Bradyrhizobium isolates.