1983 Volume 29 Issue 4 Pages 281-285
The infectivity of Rhizobium trifolii 4S (infective strain on white clover) was lost in 50% of the surviving cells when the cells were incubated in broth medium without shaking at 35° for 7 days.
The plasmid DNA extracted from 4S strain and non-infective strains (A1, spontaneous mutant obtained from 4S, and strain H1 and H2 obtained by the incubation of high temperature) were separated by 0.7% agarose gel electrophoresis. Rhizobium trifolii 4S had three plasmids with molecular weights of 210, 280 and 350Md. However, only two plasmids of 280 and 350Md were detected from the non-infective strains A1, H1 and H2.