A STUDY OF RHIZOBIUM-LEGUMINOSARUM BIOVAR TRIFOLII POPULATIONS FROM SOIL EXTRACTS USING RANDOMLY AMPLIFIED POLYMORPHIC DNA PROFILES

This study has shown that isolates of Rhizobium leguminosarum biovar t rifolii can be grouped on the basis of their randomly amplified polymo rphic DNA (RAPD) fragment patterns. Evidence is presented that these g roups are not entirely arbitrary but are consistent with other genetic and phenotypic characteristics. RAPD analysis has been used to assess the efficiency of a dispersion and differential centrifugation proced ure used to extract bacteria from soil. Whilst the major groups of Rhi zobium isolates in soils were also found in the extracts, some of the others were missing. This is also reflected in the finding, made by me asuring abundance of organisms, that as many Rhizohium isolates are le ft in the residue as appear in the supematant; more dispersion steps, possibly with different dispersants, are needed to maximize extraction . The technique has also demonstrated that dispersing soil by simply s haking it in water not only underestimates the numbers of Rhizobium is olates present but also masks much of their diversity.